Patent Description:
Many drug substances cannot be produced in the liquid form ready for application because this requires appropriate stability in an aqueous solution or even in a suspension. Such substances include antibiotics. In the case of oral or parenteral formulations, powders or granules (dry formulations) for ex tempore preparation of the liquid form are then prepared. Such an approach is impractical for eye drops because combining a powder with a solvent would require an aseptic procedure, which is not possible at the patient's home. Such formulations have occasionally appeared but have not gained popularity.

Oil-based eye drops, and thus anhydrous formulations, are known. Unfortunately, oil-based solutions administered in the eye interfere with vision and are poorly tolerated by the patient. Also oral or mucosal administration of a delivery system consisting only of a hydrophobic oil is not attractive because of its taste, organoleptic sensations and poor miscibility with body fluids.

Self-emulsifying oils (SEOs) are much better tolerated, especially after oral administration, because in contact with the tear fluid they create an emulsion system, easily dispersible. Such delivery systems, which constitute a mixture of an oil with a surfactant (up to <NUM>%) have already been tested in vitro (cellular cultures) and in vivo (rabbit eye) and their good tolerability and non-toxicity have been demonstrated [<NPL>. The emulsion system created "in situ" is particularly attractive in a situation where eye drops in the form of emulsions have already been introduced to the clinical use as medical devices (hydrating drops) or as medicinal products (with ciclosporin).

The literature defines self-emulsifying drug delivery systems as isotropic mixtures of an oil, surfactant, with a possible addition of a co-surfactant (or solubiliser) and an active substance, which can form oil-in-water type emulsions or microemulsions as a result of a gentle mixing after dilution with an aqueous phase.

Self-emulsifying oils have already been described as delivery systems for drug substances with poor solubility in water. Owing to the presence of the oil phase and surfactants (usually at least two), good solubility of substances is obtained, also when SEO is mixed with water or body fluids. Because the drug substance can be absorbed only when it exists in the dissolved form, such systems are used for increasing the absorption (bioavailability), and as a result the efficacy of drug substances that are poorly soluble in water. Another important factor is the interaction between the surfactants contained in the SEO and biological barriers (membranes) in the body, because a common phenomenon is promotion of absorption through a change in permeability of the barrier under the effect of surfactants.

In contact with an aqueous environment, the self-emulsifying oils may form emulsions or microemulsions. Microemulsion-forming systems require careful selection of the appropriate proportions of their ingredients and an addition of a co-surfactant. Depending on this, SEDDS (self-emulsifying drug delivery systems) and SMEDDS (self-microemulsifying drug delivery systems) are distinguished. Because of higher promotion of absorption, SMEDDS raise the most interest and there are also numerous patents for those systems. Unfortunately, because of the higher concentration of surfactants and the presence of co-surfactants, SMEDDS are associated with a greater risk of irritation (for example in the eye) than self-emulsifying oils of the SEDDS type.

Self-emulsifying oils may be administered orally, on the mucosa, on the skin, parenterally, into the eye and into the ear, but because of the high risk of irritation with other routes of administration, formulations for oral use are being primarily developed, which include the use of such oils as a filling in soft capsules.

Self-emulsifying drug delivery systems that contain the oil phase and more than one surfactant are known.

Patent application <CIT> applies to a self-emulsifying pharmaceutical nanocomposition containing iii) surface-active agent (surfactant); iv) co-surfactant. Additionally, in the above pharmaceutical nanocomposition the weight ratio of the above oil phase to the combination of surfactant and co-surfactant is <NUM> : <NUM> (and preferably <NUM> : <NUM>). Moreover, upon contact with the gastrointestinal tract fluid, the self-emulsifying pharmaceutical nanocomposition creates spontaneously nonoparticles of a size ranging from <NUM> to <NUM>. This composition contains an additional surfactant, which is unfavourable for the patient because of an increased risk of an irritant effect upon ocular administration.

From patent application <CIT>, the composition in the SMEDDS form is also known, which contains a unit dose of an active ingredient and of a self-emulsifying oil ingredient. Preferably, the active ingredients and the self-emulsifying oil ingredient are present in a solution or suspension. Furthermore, the patent application discloses a pharmaceutical composition in the form of a soft gelatine capsule containing a unit dose of the active ingredient and self-emulsifying oil ingredient consisting of an oil and non-ionic surfactant. The purpose of the composition according to patent application <CIT> is only to increase absorption of the active substance without noting the aspect of stability of the active substance in an aqueous environment. Furthermore, the composition discussed is intended for solubilisation of water-insoluble active substances such as diazepam. A technical issue resolved by such type of delivery systems is not only dissolution of the drug substance but also prevention of its recrystallisation after mixing with water, also at the target site of action of the formulation.

The present invention is a pharmaceutical composition in the form of a SEO -also called self-emulsifying drug delivery system (SEDDS) (<FIG>). In the delivery system, the water-soluble drug substance forms a suspension. After application to the eye, the emulsion is rapidly formed, and the drug substance dissolves in the tear fluid, rapidly or gradually. As a result, the obtained system constitutes an aqueous solution in which oil microdroplets constitute an "additive" to the solution prolonging the time the preparation remains in contact with the eye. In contrast to the above-listed inventions, and above all to the SMEDDS concept, the product developed does not serve to increase solubility of the active substance but the solution of this substance is formed after the addition of water, without the phenomenon of increased solubility because of the presence of surfactants. The above-described process of emulsifying an anhydrous delivery system in contact with an aqueous environment, with concomitant dissolution of the drug substance, may occur also after oral or mucosal administration.

The active substance suspension in an SEO is an anhydrous system which can be stored for a long time without decomposition of the drug substance. Since the drug substance is dispersed in the form of solid particles, high chemical stability is further guaranteed. Some active substances (depending on their lipophilicity and concentration) may be dissolved in such system, but it is not necessary. Many drug substances are poorly oil-soluble and thus a suspension is more universal. Drug substances that are poorly oil-soluble are often well-soluble in the tear fluid. Additionally, a suspension offers the possibility of preparation of formulations at different concentrations, without limitation by solubility.

The purpose of the present invention is to develop a new, stable pharmaceutical composition in the liquid form, containing in particular antibiotics as the active substances, the manufacture of which is uncomplicated and is possible with the use of the standard formulation methods. The drug delivery system forms an emulsion in the tear fluid, where the drug substance rapidly dissolves, attaining a high concentration. In contrast to oil-based formulations, SEO is well tolerated by the eye, which has been proven in in vivo studies.

The invention applies above all to eye drops but it may be a drug formulation administered by other routes, on condition of contact with the aqueous environment in vivo: orally, on the mucosa, parenterally. Moreover, an emulsion can be obtained ex tempore by adding the aqueous phase before the product is administered to the patient.

It is not necessary to dissolve the drug substance in the SEO - a form of suspension is obtained but the substance can also be dissolved.

The essence of the invention is a self-emulsifying pharmaceutical composition in the liquid form, comprising a delivery system for increasing chemical stability of an active substance, comprising a delivery system for increasing chemical stability of an active substance, containing as the active substance a drug substance unstable in an aqueous environment, characterised in that the drug substance unstable in the aqueous environment is a water soluble substance which is stable in aqueous solution for less than <NUM> year, wherein a dissolution of said substance requires a delivery of <<NUM> to <NUM> weight parts of water per <NUM> weight part of the dissolved substance, said composition contains the active substance in a quantity of <NUM>-<NUM> wt%, an oil in a quantity of <NUM>-<NUM> wt% and a surfactant in a quantity of <NUM>-<NUM> wt%, wherein the active substance is dispersed in a mixture of an oil and a surfactant; wherein said drug substance unstable in an aqueous environment is selected from a group comprising compounds belonging to the group of esters of carboxylic and inorganic acids, amides, nitriles, alkyl halogens, sulphochlorides, epoxides and carbamates, peptides, proteins, nucleic acids and wherein said composition is administered orally, into the eye, on the mucosa, or parenterally.

The present invention also covers the manufacturing method of a stable pharmaceutical composition according to the invention, in the liquid form, characterised in that this method consists of the following steps: mixing of the oil and surfactant, filtration at an elevated temperature, if necessary through a sterilising filter, suspending the drug substance (sterile if necessary) unstable in an aqueous environment, homogenisation of the suspension. Wherein said drug substance is a water soluble substance which is stable in aqueous solution for less than <NUM> year.

The oil used in the pharmaceutical composition according to the invention was selected from the group including soybean oil, MCT (medium chain triglycerides) oil, castor oil, peanut oil. The oil in the composition is a hydrophobic solvent or a mixture of such solvents which include natural oils, e.g. soybean oil, peanut oil, castor oil, sesame oil, or semi-synthetic oils, and also mineral and silicone oils. According to the invention, an oil selected from fatty acid esters with glycerol, fatty acids esters with aliphatic alcohols, unsaturated fatty acids and their mixtures. Viscosity of the oil may be modified, e.g. by isopropyl myristate or lipids with a higher melting point.

The composition may additionally contain an antioxidant, e.g. vitamin E or butylhydroxytoluene.

Surfactants in the composition are amphiphilic compounds used in pharmaceutical formulations as emulsifiers of w/o or o/w type, consisting of hydrophilic and lipophilic chemical groups. Hydrophilic groups include hydroxyl, acid, amine, amide, sulphate, phosphate or sulphonic groups, sugars, polyhydroxy alcohols, polyoxyethylene glycols. Lipophilic groups are aliphatic hydrocarbon chains (C8 - C20), either straight or branched, or polyoxypropylene substituents, and also alkylonaphtalene residues (alkyl groups C><NUM>), long chains of fluoroalkyl groups, polysiloxane groups. Both ingredients are linked by ester, ether or amide bonds- Surfactants can be used in the composition alone or as mixtures.

According to the invention, the surfactant should be selected from: polysorbates (fatty acid esters with polyoxyethylene sorbitan), fatty acid esters with sorbitan (e.g. Span), monoglycerides, polyoxyethylated glycerides of castor oil (e.g. Cremophor), poloxamers or their mixtures.

An active substance unstable in an aqueous environment is considered any substance that decomposes in the presence of water. With regard to the invention, these are water-soluble substances which are stable in aqueous solutions for less than <NUM> year, which means that their content at <NUM> months of storage in the refrigerator or at room temperature decreases by at least <NUM>% or the content of decomposition products exceeds <NUM>%. Such substances contain ester, amide, lactam and imide groups and belong to the group of amides, nitriles, carboxylic and inorganic acid esters, alkyl halides, sulphochlorides, epoxides and carbamates. Examples of drug substances that are unstable in an aqueous environment are antibiotics and other antimicrobial drugs, vitamins, non-steroidal anti-inflammatory agents, cytostatics, peptides, proteins, nucleic acids.

The invention is illustrated by the following examples that do not limit its scope in any way and <FIG> presenting the microscopic image of the vancomycin suspension in a mixture of the oil with surfactant (A) and after the formulation was mixed with water (B).

Polysorbate <NUM> means polyoxyethylene sorbitan monolaurate.

Polysorbate <NUM> means polyoxyethylene sorbitan monooleate.

MCT oil means medium chain triglycerides.

Cremophor EL means Polyoxyl <NUM> hydrogenated castor oil.

The oil was mixed with Polysorbate and vancomycin was added - the latter becomes suspended. The suspension was homogenised. The suspension was dispensed into tightly closed vials.

Stability of vancomycin after <NUM> months of storage at room temperature was tested. The HPLC method was used for this purpose. The comparison of the chromatogram of the formulation at time t=<NUM> and after <NUM> months did not demonstrate any additional product peaks resulting from vancomycin decomposition. <NUM>-<NUM>% of the initial content of vancomycin was determined (on the basis of the peak area).

The oil was mixed with the surfactant Cremophor EL and vancomycin was suspended. The suspension was homogenised and dispensed into vials. In tightly closed vials, the product was heated for <NUM> in an autoclave, at <NUM>.

Vancomycin stability was tested by HPLC. The comparison of the chromatogram of the formulation before heating and after autoclaving did not demonstrate any additional product peaks resulting from vancomycin decomposition. <NUM>% of the initial content of vancomycin was determined (on the basis of the peak area), evidencing the lack of decomposition in the course of thermal sterilisation.

The oil was mixed with the Span surfactant and vancomycin was suspended. The suspension was homogenised. The suspension was dispensed into tightly closed vials.

As reported in the literature, when temperature increases from <NUM> to <NUM>, the rate of active substance decomposition increases up to <NUM> times (<NPL>).

Therefore, in this embodiment example, stability of vancomycin was tested after <NUM> months of storage at <NUM>. The HPLC method was used. The comparison of the chromatogram of the formulation at time t=<NUM> and after <NUM> months did not demonstrate any additional product peaks resulting from vancomycin decomposition. <NUM>-<NUM>% of the initial content of vancomycin was determined (on the basis of the peak area).

The oil was mixed with the Cremophor surfactant, heated to <NUM> and sterilised by filtration. In aseptic conditions, sterile vancomycin was suspended. The suspension was homogenised.

The suspension was mixed with water at a ratio of <NUM>:<NUM>. A stable o/w emulsion was obtained, with an internal phase droplet size not exceeding <NUM>. Vancomycin was dissolved. The microscopic image of the vancomycin suspension in a mixture of the oil with surfactant (A) and after the formulation was mixed with water (B) is shown in <FIG> presents the <NUM>-<NUM> crystals of undissolved vancomycin suspended in the self-emulsifying oil. The self-emulsifying oil creates a uniform dispersing phase. After the addition of water, vancomycin crystals disappear because vancomycin becomes dissolved in water and the oil in the aqueous phase forms <NUM>-<NUM> droplets, creating an oil-in-water emulsion.

The oil was mixed with the Polysorbate surfactant and vancomycin was suspended. The suspension was homogenised. The suspension was dispensed into tightly closed vials.

The suspension was mixed with water at a ratio of <NUM>:<NUM>. A stable o/w emulsion was obtained, with an internal phase droplet size not exceeding <NUM>. Vancomycin was dissolved.

The oil was mixed with the Polysorbate surfactant and cefuroxime was suspended. The suspension was homogenised. The suspension was dispensed into tightly closed vials.

The suspension was mixed with water at a ratio of <NUM>:<NUM>. A stable o/w emulsion was obtained, with an internal phase droplet size not exceeding <NUM>. Cefuroxime was dissolved.

The oil was mixed with the Polysorbate surfactant and ascorbic acid was suspended. The suspension was homogenised. The suspension was encapsulated in a gelatine capsule. The capsules were stored at <NUM> for <NUM> month. Analysis of ascorbic acid using the capillary electrophoresis method was performed. No ascorbic acid decomposition products were detected.

The oil was mixed with Polysorbate. The solution was sterilised by filtration. The solution was instilled in rabbit eyes <NUM> times (every <NUM>-<NUM> hours), <NUM>µl per eye. The appearance of the conjunctiva, cornea and iris was observed for <NUM> hours after the first instillation and was scored on the Draize scale. Non-significant irritant action was demonstrated only within the conjunctiva. No reaction of the cornea and iris was detected. The MAS (maximum average score) on the scale of <NUM>-<NUM> was <NUM>.

The oil was mixed with the Cremophor EL surfactant, heated to <NUM> and sterilised by filtration. In aseptic conditions, sterile vancomycin was suspended. The suspension was homogenised.

Claim 1:
A self-emulsifying pharmaceutical composition in the liquid form, comprising a delivery system for increasing chemical stability of a water soluble active substance, a dissolution of said substance requires a delivery of <<NUM> to <NUM> weight parts of water per <NUM> weight part of the dissolved substance, said composition contains the active substance in a quantity of <NUM>-<NUM> wt%, an oil in a quantity of <NUM>-<NUM> wt% and a surfactant in a quantity of <NUM>-<NUM> wt%, wherein the active substance is dispersed in a mixture of an oil and a surfactant; wherein said drug substance unstable in an aqueous environment is selected from a group consisting of antibiotics, antimicrobial drugs, vitamins, non-steroidal anti-inflammatory agents, cytostatics, peptides, proteins, nucleic acids, said surfactant forms stable emulsions and is selected from the group consisting of polysorbates, fatty acid esters with sorbitan, monoglycerides, polyoxyethylated glycerides of castor oil, poloxamers or their mixtures; said oil is selected from fatty acid esters with glycerol, fatty acids esters with aliphatic alcohols, unsaturated fatty acids and their mixtures and wherein said composition is administered orally, into the eye, on the mucosa, or parenterally.