Patent Description:
Furosemide, an exemplary loop diuretic, can be used in the treatment of hypertension, edema and related conditions, including decompensated heart failure. Furosemide is commonly used in the treatment and/or management of edema associated with cardiac, renal, and hepatic insufficiency or failure, for example, congestive heart failure.

Oral bioavailability, and therefore oral efficacy, of furosemide is limited. Furosemide is commonly administered both parenterally and orally, although highly variable oral absorption is observed due to the combined effects of limited solubility and decreased stability at acidic pH. Accordingly, furosemide typically is administered intravenously or intramuscularly for most patients with decompensated heart failure or other forms of more advanced edema.

Intravenous administration of a pharmaceutical drug, such as furosemide, requires a trained healthcare professional for placement of the catheter and administration of the drug solution. In contrast, subcutaneous administration of a pharmaceutical drug can be accomplished with the aid of auto-injection devices and/or minipumps or subcutaneous injections or infusions, which can permit administration to be performed by the patient or caregiver, for example, at home. Subcutaneous administration of furosemide by the patient or caregiver also can allow for more optimal therapeutic administration and total dose to provide a more appropriate pharmacokinetic and pharmacodynamic profile and patient outcome.

For subcutaneous administration, discomfort and pain during administration should be minimized so as to avoid poor patient compliance with the treatment regimen. Factors that can contribute to pain and discomfort perceived by a patient upon, during, or after subcutaneous administration include the injection volume, the pH of the formulation, and the osmoticity or tonicity of the formulation. Moreover, such a formulation should be stable in solution so that it readily is available for use and/or can be pre-loaded into a variety of dispensing devices.

<CIT> discloses the tris-(hydroxymethyl)aminomethane salt of <NUM>-chloro-N-furfuryl-<NUM>-sulfamoylanthranilic acid, and pharmaceutical forms for parenteral or oral administration. Compositions including furosemide are disclosed, having a <NUM>:<NUM> molar ratio of Tris to furosemide, and a pH of between <NUM> to <NUM>.

Scientific article "<NPL>) demonstrated pH-dependent ionization of furosemide, and that the most efficient drug complexation was achieved in slightly acidic conditions (pH <NUM>-<NUM>).

<CIT> discloses parenteral solutions containing <NUM>-halo-<NUM>,<NUM>,<NUM>,<NUM>-tetrahydro-<NUM>-aryl-<NUM>-quinazoline sulfonamide in Tris or Bis-Tris or Tris buffer useful in the treatment of hypertension, heart disease and heart failure and renal disease, as well as methods for preparing such solutions.

Therefore, a need exists for improved pharmaceutical formulations containing furosemide that are stable in solution, contain a sufficient concentration of furosemide, and are at an appropriate pH and osmolality, for example, to permit subcutaneous administration of furosemide.

It has now been discovered that a stable, liquid pharmaceutical formulation including furosemide can be realized by including a molar excess of tris(hydroxymethyl)aminomethane ("Tris") to furosemide, where the concentration of Tris in the pharmaceutical formulation is in a range of about <NUM> to about <NUM>, and the pH of the pharmaceutical formulation is between about <NUM> to about <NUM>. The pharmaceutical formulations are also isoosmotic. Consequently, a stable, liquid pharmaceutical formulation results that can be appropriate for subcutaneous delivery of furosemide. Subcutaneous administration of furosemide can improve the costeffectiveness, convenience, and/or patient outcomes when compared to intravenous administration.

Accordingly, the present teachings relate to the claimed pharmaceutical formulations that include furosemide and Tris as well as to the administration of such pharmaceutical formulations. The present teachings generally can improve the pH stability and/or the active pharmaceutical ingredient ("API") stability of the pharmaceutical formulations, and/or the suitability of the pharmaceutical formulations for subcutaneous administration or delivery.

Thus, in one aspect, the present teachings provide a liquid pharmaceutical formulation for use in the treatment of edema, hypertension or heart failure or for use in the treatment of a patient exhibiting the symptoms of edema, hypertension or heart failure. The edema or hypertension can be due to congestive heart failure, or renal or hepatic insufficiency or failure. The pharmaceutical formulation is of the present teachings, where the pharmaceutical formulation includes furosemide, or a pharmaceutically acceptable salt, hydrate or ester thereof; and a pharmaceutically acceptable buffer including Tris, where the concentration of Tris in the pharmaceutical formulation is in a range of about <NUM> to about <NUM>, the pharmaceutical formulation has a molar excess of Tris to furosemide and a pH in the range of about <NUM> to about <NUM>. The pharmaceutical formulation is isoosmotic.

In particular embodiments, the formulation for use in the treatment of a patient with or exhibiting the symptoms of edema, hypertension or heart failure can include administering subcutaneously to a patient using a patch device a pharmaceutical formulation including between about <NUM>/mL to about <NUM>/mL of furosemide, or a pharmaceutically acceptable salt, hydrate or ester thereof; and a pharmaceutically acceptable buffer comprising Tris, where the concentration of Tris in the pharmaceutical formulation is in a range of about <NUM> to about <NUM>; and where the molar ratio of Tris to furosemide is greater than or equal to <NUM>, and the pharmaceutical formulation has a pH between about <NUM> to about <NUM> and is isoosmotic.

In another aspect, the present teachings provide pharmaceutical formulations including furosemide, or pharmaceutically acceptable salt, hydrate or ester thereof; and a pharmaceutically acceptable buffer including Tris in a range of about <NUM> to about <NUM>, where the molar ratio of Tris to furosemide is greater than one and the pharmaceutical formulation has a pH in the range of about <NUM> to about <NUM> and is isoosmotic.

The foregoing as well as other features and advantages of the present teachings will be more fully understood from the following figures, description, examples, and claims.

It should be understood that the drawings described below are for illustration purposes only. The drawings are not necessarily to scale, with emphasis generally being placed upon illustrating the principles of the present teachings.

The present teachings can enable the subcutaneous administration of furosemide. More specifically, the present teachings providethe liquid pharmaceutical formulations disclosed herein for use in the treatment of edema, hypertension or heart failure or for use in the treatment of a patient exhibiting the symptoms of edema, hypertension or heart failure, wherein the liquid compositions include furosemide and a buffer including tris(hydroxymethyl)aminomethane ("Tris").

For subcutaneous administration, as with any type of drug administration, pain and discomfort during administration should be minimized. To that end, the injection volume (relating to the concentration of the API in the formulation), the pH, and the osmoticity or tonicity of the formulation should be controlled to provide a liquid formulation that will assist in patient compliance with the treatment regimen. In addition, a useful pharmaceutical formulation for subcutaneous administration should be a stable, liquid pharmaceutical formulation so that it can be stored and available for use without any preparation, particularly if the pharmaceutical formulation is to be dispensed from a micropump, a patch device, or other pre-loaded device.

Accordingly, a pharmaceutical formulation should have a sufficient concentration of API so as to minimize the volume of formulation that needs to be administered subcutaneously to provide a therapeutically effective amount of the drug. The liquid pharmaceutical formulation of the present teachings has a pH between about <NUM> to about <NUM>, and the administered formulation readily can equilibrate to physiological pH. In addition, the pharmaceutical formulation isisoosmotic. Moreover, the pharmaceutical formulation should be API and/or pH stable over a sufficient time so that the formulation has a reasonable shelf life and readily can be available for use when needed.

As discussed herein, furosemide has poor water solubility. The intrinsic aqueous solubility of furosemide at room temperature has been reported to about <NUM> micrograms per milliliter ("µg/mL"). Consequently, furosemide typically requires an alkaline environment for adequate solubility and stability. The commercial formulation for injectable furosemide contains <NUM>/mL of furosemide in a saline solution adjusted to pH <NUM> - <NUM> with sodium hydroxide or hydrochloric acid, as necessary. American Reagent, Furosemide Injection, USP. Product Insert. However, such a high pH is inappropriate for subcutaneous administration.

<CIT> to Di Schiena (the "'<NUM> patent") describes the tris(hydroxymethyl)aminomethane salt of furosemide as being highly soluble in water and having a pH between <NUM> - <NUM>. The '<NUM> patent describes making the salt using a <NUM>:<NUM> molar ratio of furosemide to tris(hydroxymethyl)aminomethane and using the salt in pharmaceutical forms for injection (e.g., intramuscular and intravenous) and for oral administration. The '<NUM> patent further describes isolating the salt or disposing a solution preparation of the salt in vials suitable for injection. However, it now has been discovered that a stable, liquid pharmaceutical formulation containing furosemide that can achieve one or more of the above criteria desired for subcutaneous administration can be realized by including a molar excess of Tris to furosemide in the pharmaceutical formulation, where the pharmaceutical formulation includes a concentration of Tris is in a range of about <NUM> to about <NUM>, and has a pH between about <NUM> to about <NUM>. The pharmaceutical formulationis isoosmotic.

In certain embodiments, the pharmaceutical formulation can have a pH in the range of about <NUM> to about <NUM>, about <NUM> to about <NUM>, or about <NUM> to about <NUM>. In particular embodiments, the pharmaceutical formulations can have a pH in the range of about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, or about <NUM> to about <NUM>. In some embodiments, the pharmaceutical formulation can have a pH in the range of about <NUM> to about <NUM>, about <NUM> to about <NUM>, or about <NUM> to <NUM>.

The molar ratio of tris(hydroxymethyl)aminomethane to furosemide in the pharmaceutical formulation is greater than <NUM>. In various embodiments, the molar ratio of Tris to furosemide in the pharmaceutical formulation can be greater than about <NUM>, or greater than about <NUM>, or greater than about two, or greater than about <NUM>, or greater than about three. In particular embodiments, the molar ratio of Tris to furosemide can be greater than about <NUM>, or more.

The concentration of tris(hydroxymethyl)aminomethane in the pharmaceutical formulation is in a range of about <NUM> to about <NUM>. Further, in various embodiments, the Tris in the pharmaceutical formulation can be greater than or equal to about <NUM>. In some embodiments, the concentration of Tris can be greater than or equal to about <NUM>, greater than or equal to about <NUM>, or greater than or equal to about <NUM>. In certain embodiments, the concentration of Tris can be in a range of about <NUM> to about <NUM>, about <NUM> to about <NUM>, or about <NUM> to about <NUM>. In particular embodiments, the concentration of Tris can be about <NUM> or about <NUM>.

The pharmaceutical formulation is isoosmotic. In some embodiments, the pharmaceutical formulation can have an osmolality of between about <NUM> mOsM (or <NUM> mOsm/kg) to about <NUM> mOsM (or <NUM> mOsm/kg), about <NUM> mOsM (or <NUM> mOsm/kg) to about <NUM> mOsM (or <NUM> mOsm/kg), or about <NUM> mOsM (or <NUM> mOsm/kg) to about <NUM> mOsM (or <NUM> mOsm/kg).

In addition, the pharmaceutical formulations of the present teachings can achieve a level of solubility of furosemide that is suitable for subcutaneous administration. For example, the amount of furosemide in a pharmaceutical formulation can be about <NUM>/mL or greater, about <NUM>/mL or greater, or about <NUM>/mL or greater. In various embodiments, the amount of furosemide can be about <NUM>/mL or greater, about <NUM>/mL or greater, about <NUM>/mL or greater, or about <NUM>/mL or greater.

Some embodiments, furosemide can be present in an amount between about <NUM>/mL to about <NUM>/mL, between about <NUM>/mL to about <NUM>/mL, between about <NUM>/mL to about <NUM>/mL, between about <NUM>/mL to about <NUM>/mL, or between about <NUM>/mL to about <NUM>/mL. In some embodiments, furosemide can be present in an amount about <NUM>/mL, about <NUM>/mL, about <NUM>/mL, about <NUM>/mL, about <NUM>/mL, about <NUM>/mL, or about <NUM>/mL.

Moreover, in various compositions, and compositions for use in treatment of the present teachings, the pharmaceutical formulation can be substantially pH stable and/or API stable at room temperature for at least three months, or for at least one year. In some embodiments, the pharmaceutical formulation can be substantially pH stable and/or API stable at room temperature for at least two years, for at least three years, or more. In certain embodiments, the pharmaceutical formulations of the present teachings can exhibit an increased API stability and/or an increased pH stability at room temperature for one year and/or two years compared to a substantially identical pharmaceutical formulation but for the molar ratio of Tris to furosemide being about <NUM>:<NUM>.

In particular embodiments, the pharmaceutical formulations of the present teachings can exhibit an increased pH stability and/or an increased API stability when exposed to a temperature of about <NUM> for three months compared to a substantially identical pharmaceutical formulation but for the molar ratio of Tris to furosemide being about <NUM>:<NUM>.

In some embodiments, the pharmaceutical formulations of the present teachings can exhibit an increased API stability when exposed to light, for example, sunlight and/or white light, compared to a substantially identical pharmaceutical formulation but for the molar ratio of Tris to furosemide being about <NUM>: <NUM>. In various embodiments, the pharmaceutical formulations can exhibit an increased API stability under termination sterilization conditions, for example, dry heat sterilization, compared to a substantially identical pharmaceutical formulation but for the molar ratio of Tris to furosemide being about <NUM>: <NUM>.

In various embodiments, the pharmaceutical formulation is administered subcutaneously, for example, using a pump device such as a micropump or a patch device. However, in certain embodiments, the pharmaceutical formulation can be administered intravenously. Administering intravenously the pharmaceutical formulations of the present teachings can provide certain benefits as the pharmaceutical formulations can be at or near physiological pH and is isoosmotic as well as can include an increased concentration of furosemide.

Throughout the application, where compositions are described as having, including, or comprising specific components, or where processes are described as having, including, or comprising specific process steps, it is contemplated that compositions of the present teachings also consist essentially of, or consist of, the recited components, and that the processes of the present teachings also consist essentially of, or consist of, the recited process steps.

In the application, where an element or component is said to be included in and/or selected from a list of recited elements or components, it should be understood that the element or component can be any one of the recited elements or components, or the element or component can be selected from a group consisting of two or more of the recited elements or components. Further, it should be understood that elements and/or features of a composition, an apparatus, or a method described herein can be combined in a variety of ways, whether explicit or implicit herein.

The use of the terms "include," "includes", "including," "have," "has," or "having" should be generally understood as open-ended and non-limiting unless specifically stated otherwise.

The use of the singular herein includes the plural (and vice versa) unless specifically stated otherwise.

Where the use of the term "about" is before a quantitative value, the present teachings also include the specific quantitative value itself, unless specifically stated otherwise. As used herein, the term "about" refers to a ± <NUM>% variation from the nominal value unless otherwise indicated or inferred. For example, in certain applications, such as pH measurements, the term "about" can refer to a ± <NUM>%, or a ± <NUM>%, or a ± <NUM>% variation from the nominal value or a fixed variation from the nominal value, for example, ± <NUM> pH units or ± <NUM> pH units.

At various places in the present specification, values are disclosed in groups or in ranges. It is specifically intended that the description include each and every individual subcombination of the members of such groups and ranges. For example, an integer in the range of <NUM> to <NUM> is specifically intended to individually disclose <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, and an integer in the range of <NUM> to <NUM> is specifically intended to individually disclose <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>.

As used herein, "patient" refers to a mammal, such as a human.

As used herein, a "compound" (including a specifically named compound, e.g., furosemide) refers to the compound itself and its pharmaceutically acceptable salts such as a sodium salt or a quaternary ammonium salt, hydrates and esters, unless otherwise understood from the context of the description or expressly limited to one particular form of the compound, i.e., the compound itself, or a pharmaceutically acceptable salt, hydrate or ester thereof. Where reference is made herein to an "API," the API can be furosemide.

As used herein, "furosemide" refers to a compound having the formula:
<CHM>
and pharmaceutically acceptable salts, hydrates and esters thereof, for example, furosemide sodium salt and furosemide quaternary ammonium salt. Furosemide can be referred to by other names, for example, frusemide, <NUM>-(aminosulphonyl)-<NUM>-chloro-<NUM>-[(<NUM>-furanyl-methyl)amino]benzoic acid, or its IUPAC name, <NUM>-chloro-<NUM>-(furan-<NUM>-ylmethylamino)-<NUM>-sulfamoyl-benzoic acid, or its common trade name, Lasix®.

As used herein, a "buffer" refers to an aqueous solution that is resistant to changes in pH. A buffer can include a weak acid and its salt, or a weak base and its salt, which assist in maintaining the stability of the pH. Examples of buffers used in pharmaceutical formulations include bicarbonate buffers, carbonate buffers, citrate buffers, histidine buffers, phosphate buffers, tartrate buffers, tris(hydroxymethyl)aminomethane (or <NUM>-amino-<NUM>-hydroxymethyl-propane-<NUM>,<NUM>-diol [(HOCH<NUM>)<NUM>CNH<NUM>]) buffers, and combinations thereof. Certain of these buffers are suitable for pharmaceutical formulations administered subcutaneously.

Tris(hydroxymethyl)aminomethane or a tris(hydroxymethyl)aminomethane buffer can be referred to as "TRIS," "Tris," "Tris base," "Tris buffer," "Trisamine," "THAM," and other names. In addition, many buffers and/or buffer systems include Tris. For example, Tris-buffered saline ("TBS"), Tris-hydrochloride buffer ("Tris-HCl"), Tris base (pH <NUM>), Tris/borate/ethylene diamine tetra-acetate ("EDTA") buffer ("TBE"), and Tris/acetate/EDTA buffer ("TAE"). Tris base often is used with Tris-HCl to prepare Tris buffers at a desired pH. In addition, the present teachings include Tris-related compounds, for example, compounds derived from Tris or structurally-related to Tris, that can act as a buffer.

As used herein, "tonicity" refers to the ionic strength or concentration of ions in a solution such as a pharmaceutical formulation. Tonicity often is measured in molarity ("M"). As used herein, an "isotonic solution," an "isotonic formulation," an "isotonic pharmaceutical formulation," and a pharmaceutical formulation that is "isotonic" refers to a solution or formulation that has the same or similar concentration of ions as found in bodily fluids.

As used herein, "osmoticity" and "osmolality" refer to the osmotic pressure of a solution such as a pharmaceutical formulation. Osmoticity often is measured in osmolarity ("Osm/L" or "OsM") or osmolality ("Osm/kg"), which can be used interchangeably herein. When measuring freezing point depression, the observed value is the osmolality of the solution. In contrast to tonicity, osmoticity accounts for un-ionized solutes in a solution such that when present, the osmolarity or osmolality of the solution will be higher than its tonicity. As used herein, an "isoosmotic solution," an "isoosmotic formulation," an "isoosmotic pharmaceutical formulation," and a pharmaceutical formulation that is "isoosmotic" refers to a solution or a formulation that has the same or similar concentration of solutes as found in bodily fluids. In certain embodiments, a pharmaceutical formulation that is "isoosmotic" can have an osmolarity in the range of about <NUM> mOsM to about <NUM> mOsM or when the osmolality of the formulation is in the range of about <NUM> mOsm/kg to about <NUM> mOsm/kg.

As used herein, "pharmaceutically acceptable" refers to a substance that is acceptable for use in pharmaceutical applications from a toxicological perspective and does not adversely interact with the active ingredient. Accordingly, pharmaceutically acceptable carriers are those that are compatible with the other ingredients in the formulation and are biologically acceptable. Supplementary active ingredients can also be incorporated into the pharmaceutical compositions.

As used herein, "pH stable" refers to less than or equal to about a ± <NUM> pH value variation in the pH of a solution, for example, a pharmaceutical formulation, over time. In various embodiments, pH stable can refer to less than or equal to about a ± <NUM> pH value variation in the pH of a solution over time. In some embodiments, pH stable can refer to less than or equal to about a ± <NUM> pH value variation in the pH of a solution over time. In certain embodiments, pH stable can refer to less than or equal to about a ± <NUM> pH value variation in the pH of a solution over time. In particular embodiments, pH stable can refer to less than or equal to about a ± <NUM> pH value variation in the pH of a solution over time.

As used herein, "API stable" refers to less than or equal to about a ± <NUM> % variation in the amount of API, for example, furosemide, in a solution, for example, a pharmaceutical formulation, over time. In various embodiments, API stable can refer to less than or equal to about a ± <NUM> % variation in the amount of API in a solution over time. In some embodiments, API stable can refer to less than or equal to about a ± <NUM> % variation in the amount of API in a solution over time. In certain embodiments, API stable can refer to less than or equal to about a ± <NUM> % variation in the amount of API in a solution over time. In particular embodiments, API stable can refer to less than or equal to about a ± <NUM> % variation, or a ± <NUM> % variation, in the amount of API in a solution over time.

As used herein, "physiological pH" refers to a pH of about <NUM>.

As used herein, "therapeutic combination" refers to a combination of one or more active drug substances, i.e., compounds having a therapeutic utility. Typically, each such compound in the therapeutic combinations of the present teachings can be present in a pharmaceutical formulation comprising that compound and a pharmaceutically acceptable carrier. The compounds in a therapeutic combination of the present teachings can be administered simultaneously, together or separately, or separately at different times, as part of a regimen.

The present teachings provide pharmaceutical formulations that include furosemide or a therapeutic combination including furosemide, and one or more pharmaceutically acceptable carriers, excipients, or diluents such as a buffer. Examples of such carriers are well known to those skilled in the art and can be prepared in accordance with acceptable pharmaceutical procedures, such as, for example, those described in<NPL>)). For example, liquid media or liquid carriers (which are used interchangeably herein) can be used in preparing pharmaceutical formulations of the present teachings such as solutions, suspensions, and emulsions. A compound described herein can be dissolved or suspended in a pharmaceutically acceptable liquid carrier such as a buffer, which liquid carrier also can include an organic solvent, and/or pharmaceutically acceptable oils and/or fats.

The pharmaceutical formulations of the present teachings can include other suitable pharmaceutical additives such as solubilizers, emulsifiers, buffers, preservatives, sweeteners, flavoring agents, suspending agents, thickening agents, colors, viscosity regulators, stabilizers, and osmo-regulators. Because the present teachings provide pharmaceutical formulations and their intended use is with patients such as humans, each of the ingredients or compounds of a pharmaceutical formulation described herein can be a pharmaceutically acceptable ingredient or compound.

As described herein, the present teachings provide stable, liquid pharmaceutical formulations containing furosemide that can achieve one or more of the following beneficial characteristics for subcutaneous delivery. There is also provided such formulations for use in the treatment of edema, hypertension or heart failure or for use in the treatment of a patient exhibiting the symptoms of edema, hypertension or heart failure. The pharmaceutical formulations of the present teachings have a pH between about <NUM> to about <NUM>, accordingly a pH near or at physiological pH or at a pH that readily can equilibrate to physiological pH upon administration to a patient. The pharmaceutical formulations are isoosmotic, and can include an increased concentration of furosemide so that less volume of the liquid formulation needs to be administered per dose. The pharmaceutical formulations also can be pH stable and API stable.

A study was undertaken to determine whether a commercial formulation of furosemide for intravenous administration could be adapted for subcutaneous administration generally in view of the above beneficial characteristics.

More specifically, to confirm the insolubility and instability of furosemide in an unbuffered solution as a function of pH, a study was performed as described in Example <NUM>. It was observed that the solution pH was strongly influenced by furosemide dissolution, such that any changes in the amount of dissolved solid affected a significant change in the solution pH. The rate of dissolution was also observed to be quite slow in neutral and weakly alkaline solutions. Highly basic (pH of <NUM> to <NUM>) solution conditions were necessary to drive dissolution for concentrations as low as <NUM>/mL of furosemide.

Additionally, samples were prepared at both <NUM>/mL and <NUM>/mL furosemide and adjusted to target values in the pH range of <NUM> to <NUM> using sodium hydroxide and hydrochloric acid. The pH of these solutions was observed to be highly variable over time and as such, the solution pH was monitored for a period of <NUM> hours. Over this time, the solution pH was observed to continually decrease and a stable pH value was not achieved. The results suggest that an unbuffered aqueous solution of furosemide may be unstable with respect to pH when prepared below pH <NUM>.

To confirm these preliminary observations, the reproducibility of solution behavior at pH <NUM> was evaluated for <NUM>/mL furosemide (experimental not shown). Although all samples were prepared to contain the same equivalents of furosemide, acid, and base, the observed pH values varied widely. Thus, the formulation of furosemide in an unbuffered system is likely not feasible in the pH range of <NUM> to <NUM>.

As described in Example <NUM>, a buffer was added to furosemide solutions to determine whether the pH stability of the solutions can be improved. Sodium and potassium phosphate and Tris buffer systems were evaluated at pH values in the range of <NUM> to <NUM> and at selected buffer concentrations ranging from <NUM> to <NUM>. Buffer concentration can be an important factor when deviating from physiological pH. In such embodiments, the buffer strength can be minimized but retain its buffering capacity to permit efficient equilibration of the pharmaceutical formulation to physiological pH upon administration to a patient.

Although both phosphate and Tris buffers improved the pH stability compared to unbuffered solutions, it was discovered that the Tris buffer system maintained solution pH values closer to the nominal values than the various phosphate buffer systems evaluated. Moreover, the results unexpectedly showed that solution concentrations of up to approximately <NUM>/mL of furosemide in the target pH range could be attained.

In addition, the Tris buffer system performed better despite the significantly higher solution concentration of furosemide. That is, not only did a buffer including Tris provide a pH stable solution including furosemide, but the buffer including Tris also permitted a greater concentration of furosemide to be present in the solution, which was less alkaline and closer to physiological pH than the commercial formulations of furosemide.

Given the unexpected increase in solubility of furosemide in a buffer including Tris, the chemical stability of furosemide in buffered solutions including Tris over a pH range of <NUM> to <NUM> at ambient temperature at a solution concentration of <NUM>/mL was conducted as detailed in Example <NUM>. No decrease in furosemide concentration was observed over <NUM> hours. All pH values were within <NUM> units of the initial value.

Example <NUM> evaluated the chemical and physical stability of furosemide in buffered solutions at pH's <NUM>, <NUM> and <NUM> following short term exposure to commonly encountered storage conditions (i.e. -<NUM>, <NUM> - <NUM>, <NUM>, and <NUM>) at a solution concentration of <NUM>/mL of furosemide. No decrease in furosemide concentration was observed over <NUM> hours. All pH values were within <NUM> units of the initial value. Additionally, the osmolality was consistent over <NUM> hours. These results suggest that the Tris-buffered furosemide solutions may not be susceptible to cold-induced precipitation, as has been observed for the commercially available product.

Because <NUM>/mL furosemide solutions can be a suitable concentration for a commercial pharmaceutical product, further studies were conducted using this concentration of furosemide. Nevertheless, the results with the <NUM>/mL furosemide solutions could apply equally to other concentrations of furosemide provided the pharmaceutical formulations are in accordance with the present teachings.

Example <NUM> evaluated the chemical stability of <NUM>/mL furosemide in <NUM>, <NUM>, and <NUM> Tris-buffered, isoosmotic solutions at pH's <NUM>, <NUM> and <NUM> following three months of exposure to temperatures of -<NUM>, <NUM> - <NUM>, <NUM>, and <NUM>. After three months of storage, no change in furosemide concentration, pH, osmolality, or visual appearance was observed in any of the samples. <FIG> shows a representative HPLC chromatogram of samples of <NUM>/mL furosemide in <NUM> Tris-buffered, isoosmotic solutions stored at the various temperatures for three months. The lower trace in <FIG> is a diluent blank and the upper trace shows the retention time of furosemide to be about <NUM> minutes. These results suggest that the long term storage of the pharmaceutical formulations of the present teachings can be satisfactory for a commercial product.

Example <NUM> evaluated the chemical stability of <NUM>/mL furosemide in <NUM>, <NUM>, and <NUM> Tris-buffered, isoosmotic solutions at pH's <NUM>, <NUM>, and <NUM> following three month exposure to accelerated storage conditions (i.e., <NUM>). Accelerated storage conditions attempt to advance any deleterious effects that would result upon long term exposure of the solutions to commonly encountered storage conditions. The aggressive storage conditions can be used to identify trends in the results to inform early-on of possible direction for development of commercial products.

In particular, isoosmotic solutions containing <NUM>/mL furosemide with concentrations of Tris of <NUM>, <NUM>, and <NUM> and at pH's <NUM>, <NUM>, and <NUM> were subjected to <NUM> over three months. After <NUM> months at <NUM>, furosemide concentration and pH decreased significantly, and osmolality slightly increased. <FIG>, <FIG> and comparative <FIG> show the trends of the results more dramatically. In particular, a significant furosemide degradation product can be seen in the HPLC chromatograms at a retention time of about five minutes. Moreover, in comparative <FIG>, which are the <NUM> Tris-buffered samples, other degradation products can be seen as double peaks at a retention time between about <NUM> to <NUM> minutes. As confirmed by the analytical measurement of the concentration of furosemide in the solutions, the trends of the results show that at lower pH and at lower concentrations of Tris, the stability of the solutions is reduced.

Indeed the results show a trend which suggests that a molar excess of Tris to furosemide can be advantageous for the stability of the solution. An <NUM>/mL furosemide solution having a concentration of <NUM> Tris has a Tris:furosemide ratio of about <NUM>:<NUM>. When the concentration of Tris is <NUM>, a solution containing <NUM>/mL furosemide would have a Tris:furosemide ratio of about <NUM>: <NUM>. Accordingly, the trend of the results of Example <NUM> suggests that a higher molar ratio of Tris to furosemide can improve the stability of the liquid pharmaceutical formulations. For example, a pharmaceutical formulation can include a molar ratio of Tris: furosemide of greater than or equal to about <NUM>, greater than or equal to about <NUM>, greater than or equal to about <NUM>, greater than or equal to about <NUM>, greater than or equal to about <NUM>, or greater than or equal to about <NUM>, which can improve the stability and other beneficial characteristics of the pharmaceutical formulation.

The trends of the results also suggest a pH dependency. In particular, the results suggest that a non-acidic pH can improve the stability of the liquid pharmaceutical formulations. For example, a pharmaceutical formulation can have a pH greater than about <NUM>, greater than about <NUM>, or greater than about <NUM>, which can improve the stability of the formulation while also remaining near physiological pH. Although the higher end of the pH range to about <NUM> to about <NUM> can be advantageous for stability and solubility, a high end of the pH range of about <NUM> (or lower) is closer to physiological pH and can be advantageous for that purpose.

Consequently, the results and their trends suggest that a pharmaceutical formulation having a concentration of Tris in a range of about <NUM> to about <NUM>, a molar excess of Tris to furosemide, and within a pH range of about <NUM> to about <NUM> can provide a stable, liquid pharmaceutical formulation suitable for subcutaneous administration.

Qualitative observations were made with respect to the stability of <NUM>/mL of furosemide in <NUM>, <NUM>, and <NUM> Tris-buffered, isoosmotic solutions in a pH range of <NUM> - <NUM> after short term exposure to light. Visual inspection of the vials after light exposure showed a dark brown colored solution for the solution containing <NUM> Tris, with progressively lighter shades of brown for the <NUM> and <NUM> Tris-buffered solutions, respectively. These qualitative results correlate well with the results of the accelerated storage conditions of Example <NUM>.

Example <NUM> evaluated the dry heat sterilization of <NUM>/mL furosemide at pH <NUM> in <NUM> and <NUM> Tris-buffered solutions that were previously stored at <NUM> - <NUM> for <NUM> month. The results suggest that heat sterilization can be a feasible approach for the terminal sterilization of a pharmaceutical formulation of the present teachings.

Furosemide, therapeutic combinations, and pharmaceutical formulations of the present teachings may be for use in the treatment of edema, hypertension or heart failure or for use in the treatment of a patient exhibiting the symptoms of edema, hypertension or heart failure. The patient may be, for example, a human. As used herein, "treating" refers to partially or completely alleviating and/or ameliorating the condition and/or symptoms thereof. The present teachings accordingly include a pharmaceutical composition that includes a compound or therapeutic combination of the present teachings in combination or association with a pharmaceutically acceptable carrier for use in the treatment of a patient. Compounds and therapeutic combinations of the present teachings can be administered alone or in combination with other therapeutically effective compounds or therapies for the treatment of a pathological condition or disorder.

As used herein, "therapeutically effective" refers to a substance or an amount that elicits a desirable biological activity or effect.

The pharmaceutical formulations of the present teachings can be sterile solutions or suspensions. A sterile pharmaceutical formulation can be prepared using pharmaceutically accepted practices, for example, filtration and/or heat.

The pharmaceutical formulations can be administered parenterally, including by infusion, injection or implantation, which includes subcutaneous administration as appropriate. For example, the pharmaceutical formulations can be administered by, for example, subcutaneous injection or delivery, or intravenous injection or delivery.

A number of devices have been proposed to facilitate self-administration of a pharmaceutical formulation. The device typically includes a reservoir containing, for example, pre-loaded with, the pharmaceutical formulation to be administered. For example, a micropump can provide precise subcutaneous administration of small quantities of a liquid pharmaceutical formulation. Such micropumps can be compact and portable. Another type of device useful for subcutaneous delivery or administration of pharmaceutical formulations is often referred to as a patch device or a pump-patch device. Patch devices usually are attached directly to the skin of a patient. See, e.g., <CIT> and <CIT> to Sensile Pat AG.

Accordingly, in various embodiments, a medical device such as a micropump or patch device can include a reservoir containing a pharmaceutical formulation, a subcutaneous injection needle configured for removable insertion into skin of a patient, a micropump having an inlet in fluid communication with the reservoir and an outlet in fluid communication with the subcutaneous injection needle, a control system configured for controlling the micropump to deliver the pharmaceutical formulation from the reservoir to the subcutaneous injection needle, whereby the pharmaceutical formulation is administered subcutaneously to a patient, and a housing for supporting the reservoir, subcutaneous injection needle, micropump and control system, the housing being portable and adapted for contact with the skin of the patient. The pharmaceutical formulation contained within the reservoir can be any of the pharmaceutical formulation of the present teachings, for example, a pharmaceutical formulation comprising between about <NUM>/mL to about <NUM>/mL of furosemide, or a pharmaceutically acceptable salt, hydrate or ester thereof, and a pharmaceutically acceptable buffer comprising tris(hydroxymethyl)aminomethane at a concentration in a range of about <NUM> to about <NUM>, the molar ratio of tris(hydroxymethyl)aminomethane to furosemide being greater than or equal to <NUM>, the pharmaceutical formulation having a pH between about <NUM> to about <NUM> and being isoosmotic.

In certain embodiments, the medical device can be of a unitary construction. Such medical devices can be for a single or one-time use. In particular embodiments, the medical device can be of a multi-piece construction. In such medical devices, a disposable or a resuseable portion or component can be present. For example, a housing defining or including the reservoir can be a disposable or a reuseable component of the medical device. In some embodiments, the disposable or reuseable housing defining or including the reservoir can contain a pharmaceutical formulation of the present teachings. In various embodiments, the subcutaneous injection needle can be a disposable component of the medical device.

When the liquid pharmaceutical formulation is for use in the treatment or inhibition of a particular disease state, condition or disorder, it is understood that an effective dosage can vary depending upon many factors such as the particular compound or therapeutic combination utilized, the mode of administration, and severity of the condition being treated, as well as the various physical factors related to the individual being treated. In therapeutic applications, a compound or therapeutic combination of the present teachings can be provided to a patient already suffering from a disease, for example, bacterial infection, in an amount sufficient to cure or at least partially ameliorate the symptoms of the disease and its complications. The dosage to be used in the treatment of a specific individual typically must be subjectively determined by the attending physician. The variables involved include the specific condition and its state as well as the size, age and response pattern of the patient.

The compounds and therapeutic combinations described herein can be administered parenterally. Solutions or suspensions of these active compounds or pharmaceutically acceptable salts, hydrates, or esters thereof can be prepared in water suitably mixed with a surfactant such as hydroxyl-propylcellulose. Dispersions can also be prepared in glycerol, liquid polyethylene glycols, and mixtures thereof in oils. Examples of liquid carriers for parenteral administration include water, alcohols (including monohydric alcohols and polyhydric alcohols, e.g., glycols) and their derivatives, and oils (e.g., fractionated coconut oil and arachis oil). For parenteral administration, the carrier can be an oily ester such as ethyl oleate and isopropyl myristate. Sterile liquid carriers are used in sterile liquid form compositions for parenteral administration.

In certain embodiments, a parenteral preparation can include a preservative to inhibit the growth of microorganisms. However, in some embodiments, the parenteral preparation is preservative-free. In particular embodiments, a parenteral preparation can include a buffer as well as other suitable pharmaceutical additives mentioned herein such as solubilizers, emulsifiers, preservatives, sweeteners, flavoring agents, suspending agents, thickening agents, colors, viscosity regulators, stabilizers, and osmo-regulators.

The pharmaceutical forms suitable for injection can include sterile aqueous solutions or dispersions and sterile powders for the extemporaneous preparation of sterile injectable solutions or dispersions. In certain embodiments, the pharmaceutical form is sterile and its viscosity permits it to flow through a syringe. The pharmaceutical form should be stable under the conditions of manufacture and storage, for example, preserved against the contaminating action of microorganisms such as bacteria and fungi, if needed. The carrier can be a solvent or dispersion medium containing liquids such as water, ethanol, polyol (e.g., glycerol, propylene glycol, and liquid polyethylene glycol), suitable mixtures thereof, and vegetable oils.

The present teachings provide pharmaceutical formulations and pharmaceutical formulations for use in the treatment of edema, hypertension or heart failure or for use in the treatment of a patient exhibiting the symptoms of edema, hypertension or heart failure. The pharmaceutical formulations of the present teachings can achieve one or more of the desired characteristics for subcutaneous administration of furosemide. However, certain of the characteristics of the pharmaceutical formulations, for example, being at or near physiological pH and/or being isoosmotic, also can be desirable for intravenous and other types of parenteral administration to a patient and are within the scope of the present teachings.

The following examples are provided to illustrate further and to facilitate the understanding of the present teachings and are not in any way intended to limit the invention.

The materials, equipment, and procedures for the examples were as follows.

For Examples <NUM>-<NUM>, the following changes are noted with respect to the materials.

<NUM> monobasic sodium phosphate: A quantity of <NUM> of anhydrous monobasic sodium m phosphate was accurately weighed on an analytical balance, dispensed into a <NUM> volumetric flask, and dissolved in DI water. The flask was filled to volume with water and inverted to mix thoroughly. The pH of the resulting solution was <NUM>.

<NUM> dibasic sodium phosphate: A quantity of <NUM> of anhydrous dibasic sodium phosphate was accurately weighed on an analytical balance, dispensed into a <NUM> volumetric flask, and dissolved in DI water. The flask was filled to volume with water and inverted to mix thoroughly. The pH of the resulting solution was <NUM>.

<NUM> tribasic sodium phosphate: A quantity of <NUM> of tribasic sodium phosphate, dodecahydrate was accurately weighed on an analytical balance, dispensed into a <NUM> volumetric flask, and dissolved in DI water. The flask was filled to volume with water and inverted to mix thoroughly. The pH of the resulting solution was <NUM>.

Solutions of <NUM> phosphate were prepared by combining the component solutions in appropriate volumes to produce buffers of pH <NUM>, <NUM>, and <NUM> - <NUM> in <NUM> unit increments.

<NUM> Tris HCl: A quantity of <NUM> of Tris HCl was accurately weighed on an analytical balance, dispensed into a <NUM> volumetric flask, and dissolved in DI water. The flask was filled to volume with water and inverted to mix thoroughly. The pH of the resulting solution was <NUM>.

<NUM> Tris base: A quantity of <NUM> of Tris base was accurately weighed on an analytical balance, dispensed into a <NUM> volumetric flask, and dissolved in DI water. The flask was filled to volume with water and inverted to mix thoroughly. The pH of the resulting solution was <NUM>.

Solutions of <NUM> Tris were prepared by combining the component solutions in appropriate volumes to produce buffers of pH <NUM>, <NUM>, <NUM> - <NUM> in <NUM> unit increments, <NUM>, <NUM>, <NUM> and <NUM>.

A quantity of approximately <NUM> furosemide was dispensed into each of thirteen conical tubes and dissolved to <NUM>/mL in the appropriate volume of <NUM> dibasic sodium phosphate or the buffer of desired target pH. The resulting solutions were adjusted to the target pH values of <NUM>, <NUM>, and <NUM> - <NUM>, in <NUM> unit increments, using <NUM> monobasic, dibasic, or tribasic sodium phosphate, as necessary. All solutions were diluted to <NUM>/mL furosemide using the appropriate pH buffer.

A quantity of approximately <NUM> furosemide was dispensed into each of thirteen conical tubes and dissolved to <NUM>/mL in the appropriate volume of <NUM> Tris base or a sufficiently high pH buffer (i.e. greater than pH <NUM>). The resulting solutions were adjusted to the target pH values of <NUM>, <NUM>, <NUM> - <NUM> in <NUM> unit increments, <NUM>, <NUM>, <NUM> and <NUM>, using <NUM> Tris HCl or <NUM> N hydrochloric acid, as necessary. Specifically, addition of HCl was required to achieve pH values of <NUM> and <NUM>. All solutions were diluted to <NUM>/mL furosemide using the appropriate pH buffer.

A quantity of approximately <NUM> furosemide was dispensed into each of three conical tubes and dissolved to <NUM>/mL in the appropriate volume of <NUM> Tris base. The resulting solutions were adjusted to the target pH values of <NUM>, <NUM>, and <NUM>, using <NUM> Tris HCl or <NUM> N hydrochloric acid, as necessary. Specifically, addition of HCl was required to achieve a pH value of <NUM>. All solutions were diluted to a final target concentration of <NUM>/mL furosemide using the appropriate pH buffer. Upon preparation, samples were filtered through <NUM> nylon filters.

The osmolality values of <NUM>µL aliquots of each sample were measured by freezing point depression.

Mobile phase A, <NUM>% formic acid in water: A volume of approximately <NUM> of deionized water was dispensed into a <NUM> volumetric flask. After adding <NUM> of formic acid, the flask was brought to volume with water and inverted several times to mix thoroughly. The resultant solution was filtered through a <NUM> nylon filter.

Mobile phase B, <NUM>% formic acid in methanol: A volume of approximately <NUM> of methanol was dispensed into a <NUM> volumetric flask. After adding <NUM> of formic acid, the flask was brought to volume with methanol and inverted several times to mix thoroughly. The resultant solution was filtered through a <NUM> nylon filter.

A quantity of <NUM> of furosemide was accurately weighed on an analytical balance and dispensed into a <NUM> volumetric flask. The solid was dissolved and the flask filled to volume with methanol diluent to produce a <NUM>/mL stock solution. Linearity standards were prepared from the stock solution as described in the table below.

A study was conducted to determine the appropriate ratio of HCl to furosemide to produce aqueous solutions in a target pH range of <NUM> to <NUM>. Nine samples were prepared by dispensing <NUM> of furosemide each into nine tubes. An excess of sodium hydroxide was added to each tube, corresponding to <NUM>µmoles base per <NUM>µmole of furosemide, to ensure complete dissolution was obtained upon addition of saline. An appropriate volume of saline was added to the resulting solution targeting a concentration of <NUM>/mL. Various volumes of <NUM> N hydrochloric acid ("HCl") were added to each sample to attempt to obtain solutions of pH <NUM> to <NUM>. The results of the study are summarized in Table <NUM> below.

Clear solutions within the targeted pH range of <NUM> to <NUM> were achieved in samples <NUM> and <NUM> only, which are at the top of the desired range. Additionally, it was observed that very small changes in the quantity of acid added resulted in precipitation of solids and a disproportionate decrease in pH, as demonstrated by the difference in pH between samples <NUM> and <NUM>. These results suggest that the preparation of unbuffered furosemide solutions at the low end of the desired pH range is likely unfeasible due to the highly variable pH values obtained following addition of very similar molar equivalents of acid.

A study was conducted to determine whether a buffer would improve the pH stability of furosemide in the pH range of <NUM> to <NUM> and what buffer strength was necessary to maintain a nominal pH upon preparation of a saturated furosemide solution. Accordingly, sodium phosphate buffer, potassium phosphate buffer, and Tris buffer systems were evaluated at pH values in the target range of <NUM> to <NUM> and at selected buffer concentrations ranging from <NUM> to <NUM>.

Samples were prepared such that complete dissolution, though not anticipated, would result in a target concentration of approximately <NUM>/mL furosemide and measured for pH immediately following preparation. The results are summarized in the Table <NUM> below.

After <NUM> hours at ambient conditions, samples were centrifuged to pellet any undissolved solids and the resulting supernatant was measured for pH and concentration by HPLC. The results are summarized in Table <NUM> below.

The results suggest that both the buffer identity and strength have a significant effect on the resulting solution concentration. With respect to the phosphate buffer systems, a trend was observed such that reducing the buffer strength resulted in a corresponding increase in furosemide solubility. The trend appears to correlate with the ionic strength of the buffer solutions.

The Tris buffer system was observed to maintain solution pH values that were closer to the nominal values than the various phosphate buffer systems evaluated even though the solution concentration of furosemide was significantly higher in the Tris solutions. More specifically, the results suggested that solution concentrations of up to approximately <NUM>/mL of furosemide could be achieved. Additionally, the pH <NUM> Tris solution was capable of maintaining significantly higher solution concentrations than phosphate buffer solutions at comparable pH and ionic strength.

A study was conducted to evaluate the chemical and physical stability of <NUM>/mL furosemide Tris-buffered solutions over a pH range of <NUM> to <NUM> at ambient temperature. Although the results in Example <NUM> suggested that solution concentrations of about <NUM>/mL of furosemide could be attained and that these samples were not saturated at this concentration, a lower concentration that may be more appropriate for a pharmaceutical formulation was selected for evaluation.

A quantity of approximately <NUM> furosemide was dispensed into each of thirteen conical tubes and dissolved to <NUM>/mL in the appropriate volume of <NUM> Tris base or a <NUM> Tris buffer having a pH between <NUM> to <NUM>. The resulting solutions were adjusted to the target pH values of <NUM>, <NUM>, <NUM> to <NUM> in <NUM> unit increments, <NUM>, <NUM>, <NUM> and <NUM>, using <NUM> Tris HCl or <NUM> N HCl, as necessary. All solutions were diluted to <NUM>/mL of furosemide using the appropriate pH buffer. Upon preparation, samples were analyzed for concentration and purity by HPLC and for pH. Samples were stored at ambient temperature and subsequently analyzed after <NUM> and <NUM> hours of storage. The concentrations and pH values are summarized in Table <NUM> and Table <NUM>, respectively.

No decrease in sample concentration was observed over <NUM> hours. All pH values were within <NUM> units of the initial value.

A study was conducted to evaluate the chemical and physical stability of furosemide in Tris-buffered solutions at pH's <NUM>, <NUM>, and <NUM> following short term exposure to commonly encountered storage conditions (i.e., -<NUM>, <NUM> - <NUM>, <NUM>, and <NUM>). A quantity of approximately <NUM> furosemide was dispensed into each of three conical tubes and dissolved to <NUM>/mL in the appropriate volume of <NUM> Tris base. The resulting solutions were adjusted to the target pH values of <NUM>, <NUM>, and <NUM>, using <NUM> Tris-HCl or <NUM> N HCl, as necessary. All solutions were diluted to a final target concentration of <NUM>/mL furosemide using the appropriate pH buffer. Upon preparation, samples were filtered through <NUM> nylon filters and analyzed for concentration and purity by HPLC, and for pH and osmolality. Aliquots of each sample were stored at each condition and subsequently filtered and analyzed after <NUM> and <NUM> hours of storage. The results are summarized in Tables <NUM>-<NUM> below.

No decrease in furosemide concentration was observed over <NUM> hours. All pH values were within <NUM> units of the initial value. Additionally, the osmolality of the solutions was consistent over <NUM> hours. These results suggest that the Tris buffered furosemide solutions may not be susceptible to cold-induced precipitation, as has been observed for the commercially available product.

A longer term stability study was conducted to evaluate the chemical stability of <NUM>/mL furosemide in Tris-buffered (<NUM>, <NUM>, and <NUM>), isoosmotic solutions at pH's <NUM>, <NUM>, and <NUM> upon storage at temperatures of -<NUM>, <NUM> - <NUM>, <NUM>, and <NUM>. After three months of storage, samples were removed from their respective storage conditions and equilibrated to room temperature, filtered, and the supernatant tested for concentration and purity by HPLC, and for pH and osmolality. The results are summarized in Tables <NUM>-<NUM> below and generally in <FIG>.

After three months of storage, no change in furosemide concentration, pH, osmolality, or visual appearance was observed in any of the samples.

A study was conducted to evaluate the chemical stability of <NUM>/mL furosemide in Tris-buffered (<NUM>, <NUM>, and <NUM>), isoosmotic solutions at pH's <NUM>, <NUM>, and <NUM> upon storage at a temperature of <NUM>. After three months of storage, samples were removed from the storage conditions and equilibrated to room temperature, filtered, and the supernatant tested for concentration and purity by HPLC, and for pH and osmolality. The results are summarized in Tables <NUM>-<NUM> below and in <FIG>, <FIG>, and comparative 4A-4C.

After <NUM> months of storage at <NUM>, furosemide concentration and pH decreased significantly, osmolality slightly increased, and the samples were observed to be dark brown in color.

A study was conducted to evaluate the dry heat sterilization of <NUM>/mL furosemide in <NUM> and <NUM> Tris-buffered solutions at pH <NUM> that were previously stored at <NUM> - <NUM> for <NUM> month. The solutions were analyzed in triplicate for concentration and purity before and after sterilization at <NUM> for <NUM> hour.

Claim 1:
A liquid pharmaceutical formulation for use in the treatment of edema, hypertension or heart failure or for use in the treatment of a patient exhibiting the symptoms of edema, hypertension or heart failure,
wherein the liquid pharmaceutical formulation comprises:
a therapeutically effective amount of furosemide, or a pharmaceutically acceptable salt thereof; and
tris(hydroxymethyl)aminomethane, wherein the concentration of tris(hydroxymethyl)aminomethane in the liquid pharmaceutical formulation is in a range of about <NUM> to about <NUM>;
wherein the liquid pharmaceutical formulation has a pH between about <NUM> to about <NUM>, is isosmotic, and the molar ratio of tris(hydroxymethyl)aminomethane to furosemide is greater than one.