Stable aqueous suspension of mesalazine for topical use

Abstract: The invention discloses new compositions of mesalazine in the form of aqueous suspensions characterized in that they are more stable than those of the prior art.

Description: Mesalazine ( D.C.I.), or mesalamine ( USAN), is the internationally adopted name for 5-aminosalicilic acid or 5-ASA. Said compound is the active principle of pharmaceutical compositions for the therapy of Crohn's disease. Said pharmaceutical compositions are usually administered rectally, in the form of enemas, in order to provide a quicker therapeutic effect, since the active principle can act directly on the intestine mucosa just from its delivery ( A.B.R. Thompson " New development in the use of 5-aminosalycilic acid in patients with inflammation bowel disease " Aliment. Pharmacol. Therap. 1991; 5 449-470). Enemas containing mesalazine are in the form of aqueous suspensions since water solubility of the active principle is quite scanty at physiologic or slightly acidic pH's. As a consequence of it the main issue to be solved is that of the intrinsic lack of stability of said compositions. The preparations of mesalazine in the form of aqueous suspensions disclosed in the literature of the field and/or currently sold on the market are being compounded following the teachings of the art that, as it will be here below shown, don't provide a satisfactory solution for that it concerns the stability of said compositions. Said formulations contain thickening agents, sometimes also surface active agents, and antioxidants ( metabisulfite salts, usually having as the cation sodium or potassium ions), bacteriostatic and sequestering agents ( EDTA ). Other usual excipients are inorganic acids or acetate buffers, wherein the salt cation is sodium or potassium. Mesalazine suspensions for topical use according to the present invention provide an expedient solution to the afore stated stability issue since they stay homogeneous longer than those of the prior art. This latter circumstance affords the further advantage of avoiding the patient's direct intervention for homogenizing extemporarily the formulation prior of topical application, as it is moreover recommended in the package inserts of mesalazine enemas. According to the invention the above put forward stability issue is solved by formulating mesalazine with selected quantities of colloidal cellulose and of hydrophilic thickening agents in aqueous suspensions. Owing to said excipients the new liquid formulations show a thixotropic behaviour. Hence by applying a low shear to said colloidal solutions after storage for a period of time it is found that they exhibit absolute viscosities in the order of some thousands of mPa.s . Instead, when they are stirred and submitted to a moderate or high rate of shear ( the latter event taking place, by example, when the composition is being dispensed from a pressurized packaging or a plastic squeeze bottle ), said suspensions become very flowing liquids with a viscosity of a few mPa.s. Said latter property of being a flowing liquid appears indeed to be an important feature of mesalazine enemas in view of the fact that they must have, and indeed they show, a very good spreading inside the large intestine ( ref. I.R. Wilding et Alii " Colonic spreading of a non-chlorofluorocarbon mesalazine rectal foam enema in patients with quiescent ulcerative colitis " Aliment. Pharmacol. Ther. 1995 . 9 161 - 166; R.A. Vitti et Alii " Quantitative distribution of radiolabeled 5-aminosalicylic acid enemas in patients with left-sided ulcerative colitis " Digestive Diseases and Sciences vol. 34 11 1792-1797 1989; M. Campieri et alii " Spread and distribution of 5-ASA colonic foam and 5-ASA enema in patient with ulcerative colitis " Digestive Diseases and Sciences 37 12 1890- 1897 1992; M.M.C. van Buul retrograde spread of therapeutic enemas in patients with inflammatory bowel disease " Hepato-Gastroenterol. 36 ( 1989 ) 199-201). In order to arrive at the invention the applicant formerly did a thorough analytical work, performing the physical determinations and chemical analyses further on here below listed on the compositions of the prior art featured in Table I. From said work it came out the conclusion that it is indeed desirable in this technical field to make available stable aqueous suspensions of mesalazine. Coming now in detail to Table I, composition A is known from the patent application WO 92/12758 ( page 18 ). Thereof preparation and subsequent packaging in pressurized containers is described under example 1. Compositions B and C are pharmaceuticals currently available in Italy. In Table II are reported the results obtained by performing the following physical determinations and chemical analyses A. The volume, or the corresponding weight, of the mesalazine suspension obtained by opening the container and collecting the formulation in a beaker. For formulation A and C said determination was carried out by weighing the container before and after being emptied. In the case of formulation B the density of the suspension was Compositions of the mesalazine aqueous suspensions of the art being referred to in the disclosure of the invention. Excipient Compound Formulation A (w/w%) Formulation B (w/v%) Formulation C (w/w%) Mesalazine 6.67 4 6.67 THICKENING AGENT Colloidal silica - 1.7 - Xantan Gum - - 0.25 Polyvinylpyrrolidone - 0.84 - Carbopol® - - 0.075 Methylcellulose - 0.84 - Hydroxyethylcellulose 1.20 - BACTERIOSTATIC AGENT Sodium benzoate - 0.38 0.1 SEQUESTERING AGENT EDTA disodium salt 0.1 - 0.1 ANTIOXIDANT Potassium metabisulfite - 0.25 0.47 Sodium metabisulfite 0.5 - - Potassium acetate - - 0.41 Sodium acetate 0.82 - - Phosphoric acid - 0.1 - Acetic acid enough - - SOLVENT Distilled water enough to g 100 enough to ml 100 enough to g 60 CONTAINER Pressurized aluminium container Plastic squeeze bottle Plastic squeeze bottle Mesalazine aqueous suspensions of the art of Table I. Recovery tests from thereof packages and determination of the quantity of the active principle. Formulation A Formulation B Formulation C Time elapsed from the manufacture of the preparations under test. 16 months 21 months 18 months 1) Recovery of the formulation after opening the containers: - Quantity ( by weight or volume ): 61.7 g 102 ml 61 g - Active principle content ( % w/w or w/v ): 6.67 4.08 6.76 2) Recovery of the formulation dispensed from the containers: - Quantity ( by weight or volume ): 59.2 g 91.2 ml 48.9 g - Ratio as % ( w/w or w/v) of said quantity to that of the recovery under 1): 95.9 89.4 80.2 - Active principle content ( % w/w or w/v ) : 5.10 3.84 7.34 3) Recovery of the formulation left in the containers after dispensing: - Quantity ( by weight or volume): 1.98g 8.8 ml 11.5 g - Ratio as % ( w/w or w/v ) of said quantity to that of the recovery under 1): 3.2 8.6 18.8 - Active principle content ( % w/w or w/v): 39.30 7.27 4.43 4) Total grams recovered of the active principle / grams of mesalazine recovered under point 1): 0.92 0.99 0.99 determined in order to convert the obtained weight into the corresponding volume. B. HPLC assay of the active principle content in formulations A, B and C, performed as here below further on described. The results obtained with said analyses are given under point 1) of Table II. C. The weight or volume of suspension obtained by emptying the containers according to the following procedures : By pressing the valve at the top of the container in the case of formulation A. By squeezing the plastic bottles in the case of formulations B and C . The volume of formulation B was determined after assay of thereof bulk density. D. The quantity of mesalazine contained in said recovered suspensions. Thereof results are given under point 2) of Table II. E. The residual volume of formulation left in the package and thereof contained quantity of the active principle ( Ref. point 3 of Table II). The data of Table II represent the average of nine determinations, performed on three different samples, by repeating in triplicate the assay on each of them . Thorough shaking of the suspensions was made prior of said determinations. Assay of the active principle was made by HPLC on a liquid chromatograph equipped with a column Whatmann® Partisil® 100 SCX 25 length, thermostatted at 25°C and equilibrated at a flow rate of 1 ml/min. UV detector was set at a wavelength of 300 nm. The mobile phase, referred to herein also as solvent solution or solvent, was prepared by dissolving 8.38 g NaH 2 PO 4 in 1.9 I of bidistilled H 2 O and adding, when a dear solution was obtained, 80 ml of acetonitrile. pH was corrected to a value of 2.0 ± 0.1 with concentrated phosphoric acid. The solution was brought to the volume of 2 I with bidistilled water and afterwards degassed. The standard solution of mesalazine was prepared by weighing directly in a 50 ml volumetric flask about 46 mg of mesalazine with a known titer, and then diluting up to volume with the solvent. The suspension thus obtained was sonicated until a clear liquid was obtained. 1 ml was diluted in a 50 ml volumetric flask up to volume with the same solvent. The sample concentration was of 0.0184 mg/ml. For assaying mesalazine in compositions A and C, about 700 mg of each formulation ( containing 46 mg of the active principle were weighed in a 50 ml volumetric flask and diluted to volume with the mobile phase. Complete solubilization of said formulations was achieved by applying, alternatively, sonication and stirring. 1 ml was pipetted out and diluted up to volume in a 50 ml volumetric flask with the solvent. The theoretical mesalazine concentration in said samples was hence about the same than that of the standard solution. In the liquid chromatograph were then injected, in the order, the standard solution and the enema samples diluted as here above described. For formulation B the analytical procedure was somewhat different. Beforehand density of the sample was determined by means of a 25 ml picnometer. The first dilution step was effected as here above described for sample A and C. The second dilution was instead carried out in a 30 ml volumetric flask. Data given in Table II clearly show that mesalazine aqueous suspensions of to the prior art become unstable, with concomitant precipitation of a solid residue containing remarkable quantities of the active principle within a period varying from 1 to 2 years. From the same Table it is also drawn that after said precipitation the concentration of the active principle in the supernatant became different from the one reported on the package label ( ref. Table I ). For that it concerns the teachings of the prior art about the compounding of aqueous suspensions for pharmaceutical use in the book " Remington : The Science and Practice of Pharmacy- Nineteenth Edition ", volume II pages 1515 -1516 it is stated that the most important excipients of said formulations are the viscosity agents and the surface active agents, the latter being functional to wet solid particles. In said reference are also given the following recipes, that accordingly can be used for the extemporaneous preparation of aqueous suspensions : A. Sodium carboxymethylcellulose 2.5%, tragacanth gum 1.25% and guar gum 0,5%. B. Avicel® RC 591 ( colloidal cellulose, a co-precipitate of microcristalline cellulose and sodium carboxymethylcellulose ) stabilized with hydroxypropylmethylcellulose, i.e. a thickening agent, being used as a suspending vehicle for propanolol and orphenadrine hydrochloride dispersions prepared from tablets. C. Carbopol® 934, at concentrations of 0.3% or greater, being used as a vehicle for suspending sulfamethazine 10% in water. The here above cited prior art provides information for compounding suspensions being therein defined as extemporaneous, which means that they don't to have a long shelf life. For that it concerns in particular the recipes under points A and C, which are addressed to the preparation of suspensions made by using thickening agents or mixtures thereof, the applicant has demonstrated in the experiments that will be described here below that said excipients alone don't make mesalazine suspensions stable. Hence even in the case of composition C, which comprises a thickening agent together with sulfamethazine, which is slightly soluble in water at neutral pH's and behaves in this aspect like mesalazine, no useful teachings can be drawn for compounding a stable mesalazine liquid composition. For what it concerns the inclusion of a surface active agent in the formulation the applicant has further on here below demonstrated that said excipient is uninfluential on the stability of mesalazine suspensions. It is instead undeniable that the recipe given under point B discloses the same excipients as those of the composition of the instant invention. On the issue the following considerations are believed to be of value for deciding about the novelty and inventive step of this application in view of said latter teachings : Differently from mesalazine, both propanolol and orphenadrine hydrochloride are soluble in water ( ref: Index Merck 10a Edition page. 7743 n. 7740, and page 6749 n. 6752 respectively). In other words, what it has been suspended with the above recipe are the excipients of the tablet formulations and not thereof active principles. Said excipients very likely can be identified with the usual water insoluble, or slightly water soluble common tablet excipients, i.e. diluents as kaolin, starch, etc., lubricants as magnesium or calcium stearate, etc. The information provided in the above reference does not disclose any selected quantity of colloidal cellulose and hydroxypropylcellulose. Hence the variation ranges of said components in the formulations of the instant invention could not at all be anyway foreseen on the basis of said reference. Furthermore the instant limits, as it will be shown herein later on, are critical in order to ensure both the stability of the suspension and the thixotropic effect, in particular the remarkable fall of viscosity under high rate of shear formerly above outlined, that is featured herein later on in quantitative terms. EPA 0398207 discloses 5-ASA solutions containing the active principle together with its alkali metal or alkaline earth metal salt, an antioxidant and a metal complexing agent. EPA 0468555 discloses a formulation in the form of a fluid vehicle able to generate a foam on rectal administration. Said suspension comprises at least one surfactant, a foaming propellant, a suspending or solubilizing agent for the active principle and a foam thickener. USA 4,657,900 discloses an aqueous suspension of 5-ASA containing 0.25% bisulphite, being stored in a single dose polyethylene bottle in a substantially oxygen-free atmosphere, the plastic bottle being hermetically sealed in a plastic pouch. The disclosed compositions may also contain a natural or synthetic gum at concentrations form about 0.1% to 0.25% and also a flocculating agent to prevent caking of 5-ASA, such as a water gellable cross linked polyacrylic acid at a concentration of about 0.05% - 0.15%. USA 4,664,256 discloses a packaged enema solution or suspension consisting of 5-ASA, an antioxidant, a chelating agent and a buffering agent. The formulation is stored in a plastic bottle under an inert gas, being packaged in diffusion-tight light impervious bags made substantially of plastic aluminium laminate. WO 91/01129 discloses a solid composition for rectal administration that can be reconstituted immediately before use by addition of water. Said solid composition may contain different active principles, amongst which mesalazine, and an antifoam additive. a thickening agent, amongst which worth mentioning herein are the cellulose derivatives, and besides other excipients such as wetting agents, compounds for adjusting the solution isotonicity and osmolarity, diluents and low volatile liquids such as glycerine, polypropylene glycol, etc. Example 3 discloses solid compositions containing 5-ASA, sodium lauryl sulphate, hydroxypropylmethylcellulose and polydispersed silica gel. Example 4 discloses a solid composition containing 5-ASA, vinylpirrolydone/vinyl /vinyl acetate copolymer, hydroxypropylmethylcellulose, sodium lauryl sulfate and an anti foaming agent. All of the above prior documents fail to disclose a thickening agent in combination with colloidal cellulose, which taken together stabilize mesalazine suspensions and hence afford to yield an homogeneous colloid system. On this issue worth observing is that USA 4,657,900 discloses instead a thickening agent ( a natural or synthetic gum ) in combination with a flocculating agent, i.e. a substance which brings about flocculation of the suspension ( ref. the book " Remington's Pharmaceutical Sciences - fifteenth edition " page 325 ). In other words said prior teaching goes in the opposite direction than that of the instant invention. For that it concerns again WO 91/01129 worth adding herein is that the therein disclosed feature on addition of water made substantially at will in order to suspend the starting solid formulation, renders idle and void the relevance of said document as pertinent prior art of the present invention. In order to arrive at the composition of the invention the applicant formerly performed stability tests on formulations obtained by modifying composition A of Table I, which was chosen for this purpose since it was reputed the simplest to be prepared among those featured. The modifications being then made were substantially conforming the teachings of the here above mentioned book" Remington : The Science and Practice of Pharmacy, 19th edition ". The conclusions arrived at were the following: It is not possible, as detailed in example 2, to make stable mesalazine aqueous suspensions using thickening agents only. It was in fact experienced that even making about twice ( i.e. 2.2% w/w ) the quantity of hydroxyethylcellulose in the confront of that present in the original formulation A, although the suspension thus obtained was in the form of a thick gel with an absolute viscosity value ranging in the order of some thousands mPa.s, said formulation was still unstable. It was indeed observed that after conditioning in sealed glass containers at room temperature, for 1 month in the dark, a precipitate was separated. Said lack of stability was further confirmed by assaying the active principle in the supernatant gel, which titer was found lowered to 92.9 % in the confront of that determined on the fresh formulation. Addition to formulation A of a surface active agent, as detailed in example 3, doesn't either appear to improve significantly the stability of mesalazine suspensions. Said example describes the preparation of an enema suspension obtained by increasing up to 2.0% in formulation A the quantity of hydroxyethylcellulose and adding then Tween® 20 in the amount of 0.25% w/w. In this case stability was qualitatively assayed by centrifuging at 4000 rpm for 15 minutes an aliquot of the suspension, inspecting afterwards the bottom of the test tubes. It was thus noted the presence of a precipitate. The titer of the active principle in the supernatant was found to be as low as 74,35% of the theoretical calculated on the basis of the amount of mesalazine used in the preparation. The problem of obtaining aqueous suspensions of mesalazine endowed with an improved stability in the confront of those of the prior art has now been solved, according to the applicant's findings, by compounding the aqueous suspensions of said active principle with a quantity of colloidal cellulose ranging from 1.2 to 1.6% (w/v of the composition ), together with one or more hydrophilic thickening agents in a ratio by weight (w/w) to colloidal cellulose comprised between 0.04 and 0.2, corresponding respectively to a percentage of 4% and 20%. the above range becomes, or is equivalent to, 0.048 - 0.32 % w/v when the weight of the thickening agents, calculated on the lower and upper limit of the colloidal cellulose range, is instead divided by the total volume of the formulation and the relevant percentages then determined. Colloidal cellulose, otherwise defined as water dispersible cellulose, is a mixture of cellulose with 8.3 - 18.8% w/w of carboxymethylcellulose ( ref. Handbook of Pharmaceutical Excipients Second Edition 1994 page 86 ) . Suitable examples are Avicel RC 591®, Avicel RC 581®, Avicel CL-61®. The thickening agents useful for the purposes aimed to by the instant invention are the hydrophilic polymers chosen in the group consisting of the following : carboxypolymethylene, sodium carboxymethylcellulose, hydroxyethylcellulose, xantan gum, hydroxypropylmethylcellulose, methylcellulose, carrageenan. The suspension according to the present application contains also the usual excipients such as antioxidants, sequestering and bacteriostatic agents, additionally buffering agent, inorganic acids. pH is comprised between 4.5 and 5.1. The variation ranges of colloidal cellulose and of the thickening agents have been determined from the results obtained in the experiments and analytical determinations here below described. In the first set of tests, detailed under Example 4, were prepared 99 different aqueous suspensions, each in the quantity of 1 litre and containing different concentrations of colloidal cellulose and of the hydrophile thickening agent. In order to prepare them at first were compounded nine suspensions, each containing colloidal cellulose in the relevant percentages w/v ( final concentration in 1 litre ) of 1; 1.1; 1.2; 1.3; 1.4; 1.5; 1.6; 1.8; 2.0 %. From each of said nine suspensions were prepared eleven further formulations containing a thickening agent ( hydroxyethylcellulose ) in the following relevant percentages by weight referred to colloidal cellulose : 2; 4; 6; 8; 10; 12; 14; 16; 18; 20, 25 % . Mesalazine and the other excipients were added as described in the same Example 4. 500 ml of each of the final 99 suspensions was transferred into capped glass containers having a diameter of 46 mm and height 56 mm ( internal dimensions ), while with the left 500 ml aliquot were filled 20 ml syringes ( Steringa® Artsana, Casnate - Como ) having a 1.2 mm ( inner diameter ) x 38 mm ( length ) needle. The needle holder, forming one body with the flat bottom of the syringe, had an internal diameter of 2.4 mm. Both the syringes and containers were then conditioned in the dark for one month at the following temperatures : 3°C, ambient temperature, 30°C and 40°C. Inspection of the content of the glass containers at the end of this period evidenced that a precipitate was present at the bottom of those glass containers filled with formulations having a quantity of colloidal cellulose below 1.2% w/v. The precipitate was abundant in those suspensions conditioned at temperatures of 30°C and 40°C. It was also ascertained that the phenomenon was independent of the added quantity of the thickener. It was furthermore assessed that a quantity of cellulose above 1.2 % w/v wasn't by alone enough to provide the awaited stability, if concomitantly the weight ratio of the thickening agent to colloidal cellulose wasn't of 4 % or higher. In the case of 1.2% w/v of cellulose that weight ratio of the thickener to said excipient corresponded to a percentage of 0.048 % w/v on the total volume solution. It was also observed that at concentrations of colloidal cellulose higher than 1.6 % w/v the suspensions retained a high viscosity and the compositions looked of a gel-like consistency after being manually extruded from the syringes and did not show the thixotropic behaviour of the enemas of the invention. It was also noted that by increasing the weight ratio of the thickening agent in the confront of cellulose above 20% w/w, or above 0.32 % w/v calculated on the overall suspension in the case wherein the colloidal cellulose quantity was of 1.6% w/v, the extruded liquids resumed very quickly high values of viscosity. This was not considered desirable in view of the fact that mesalazine enemas are generally low viscous liquids, and moreover upon consideration of the results obtained in the clinical pharmacological trial reported under Example 7, which demonstrates that the formulations of the invention behave substantially as the mesalazine suspensions of the art. The latter circumstance suggested that very probably the enemas of the invention are able to retain low viscosities even for a fair long time. It was hence concluded that it is indeed of importance that the new mesalazine thixotropic compositions should contain colloidal cellulose and the thickening agent in relevant quantities such as to be comprised between the instant ranges. Reverting to the experiments performed by the applicant on the formulations of Example 4, worth noting is that a few syringes taken from the lots containing a quantity of colloidal cellulose comprised between 1.2 and 1.6% and of the thickener between 4% and 20% ( as percentage weight ratio to cellulose ), after removal of thereof needle were emptied in 4 seconds or less by applying to the plunger a weight comprised between about 970 and 1100 mg. Absolute viscosity determinations performed on the same suspensions afforded to establish that the formulations satisfying the here above referred to qualitative test had an absolute viscosity of 7 mPa.s or lower when measured at the shear rate of 37,6 sec -1 at the temperature of 20°C. The viscometer used was a rotational viscometer Contraves Low Shear 30 equipped with the measuring bob n. 1, dimensions Ø 11 X 8 mm. The instrument was set on range 3, corresponding to a shear stress τ Pa 1% 0,01305. The volume of the formulations used for said determinations was of about 700 µl. Worth noting is that absolute viscosities in the same conditions of compositions B and C (ref. Table 1) were very near to the above limit. Reverting now to the further research work made on the instant formulations, in a second series of experiments it was scrutinized more in detail which was the composition of the suspension that gave the best behaviour in the syringe test . According to the same recipe given in Example 4, were prepared at first n. 5 suspensions containing colloidal cellulose at concentrations, respectively, of 1.2; 1.3; 1.4; 1.5; 1.6% w/v. From each of said suspensions were then made up 7 formulations containing a quantity of hydroxyethylcellulose in the lower half of the selected range, i.e. as w/w percentage to colloidal cellulose, of 4, 5, 6, 7, 8, 9, 10 % respectively. As a whole were hence prepared n. 35 samples. From the results obtained it was concluded that the compositions with very good thixotropic behaviour and flowing properties contained 1.4% w/v of colloidal cellulose and a quantity of thickening agent varying from 6% to 7% by weight in the confront of that of cellulose or, otherwise said, in a percentage w/v on the overall composition from 0.084 to 0.098 % ( calculated on 1.4% w/v of colloidal cellulose). Taking into account the results obtained in the aforementioned experiments it was decided to carry out a second series of stability tests, performed at room temperature for a time longer than before, in order to check which was the actual shelf life of the new compositions. Three lots of enema formulations, which composition is given in Table III, were prepared according to Example 5, on the basis of the indications given in Example 4. The enemas were packed in pressurized containers under nitrogen gas by the same procedure described in the second part of Example 1. Each container was filled with a volume of enema of 60 ml, corresponding to 62 g of the formulation as established by thereof former density determinations. Said quantity of 62 g was hence the theoretical content of each packaging on the basis of the recipe used to prepare said suspensions. The filled containers were then conditioned at room temperature. n. 3 samples were then taken for analysis at the time zero and then, respectively, after one and two years. The suspensions were discharged from the containers by pressing the valve stem and thereof weight and active principle content then determined. It was checked also the weight of the residual suspension in the container. In order to carry out this latter assay the packagings were emptied by pressing the actuator, then carefully weighed, opened and washed out with water and aqueous ethanol. Afterwards they were dried in an oven at 30°C and weighed again. The results of stability tests given in Table IV evidence that the new compositions of mesalazine are stable for two years. One further embodiment of the application is the process for manufacturing the new aqueous suspensions of mesalazine. Said process, as from example 6, consists of the following steps : Dissolution of colloidal cellulose and of the thickening agent in two separate aliquots of distilled water, the latter being in the percentage respectively of 60% and 30% of the total volume of water needed for the preparation. Mixing said two solutions and addition of the other excipients of the formulation. Addition and suspension in said solution, under vacuum and stirring, of the active principle. Addition to the aqueous suspension of distilled water in order to yield the final requested volume. The new formulations may be stored in squeeze bottles containing in a volume of 60 ml 2 or 4 g of mesalazine, or in containers pressurized with nitrogen . In the latter case particularly suitable are containers having inside a smaller bag filled with the suspension, made of a thin aluminium foil being covered on both sides with plastic coatings. In this way the suspension is hermetically insulated from the propellant, so that the latter is excluded, as in many aspects it is advantageous it should be, from being delivered into the intestine together with the formulation during dispensing from the pressurized containers. Coming to consider Figure 1, curves A, B and C show the different rheological behaviour ( in ordinates the shear stress in Pascal and in abscissas shear rate in s -1 ) of three compositions. Curve A refers to a formulation according to the instant invention having the composition of example 8, curves B e C refers to the formulations B and C featured in Table I. Said diagrams were obtained using the same rotational viscometer ( Low Shear 30 ) described previously, and the same volume of solution in the measuring cup. The temperature was fixed at 20°C. The range on which the instrument was set ( range 5 ) corresponds to a shear stress τ Pa 1% 0,0326. Each point of the curve is the average of 18 separate determinations taken on the sample at intervals of 15 seconds. The sample was at first equilibrated for about 10 minutes in the measuring cup with the measuring bob dipped into the solution, rotating at the selected shear stress. Within said time readings became fairly constant. Curve A features the thixotropic properties of the suspensions according to the invention. Curves B e C show that the suspensions of the prior art containing mesalazine differ in that they don't share, or do share only at some extent, said property. Composition w/v of the formulations used in the second series of stability tests . Form. I A Form. I B Form. I C Form. II A Form. II B Form. II C Form. III A Form. III B Form. III C Mesalazine 6.67 6.67 6.67 6.67 6.67 6.67 6.67 6.67 6.67 Colloidal cellulose(C.C.) 1.2 1.2 1.2 1.4 1.4 1.4 1.6 1.6 1.6 Hydroxyethyl cellulose(H.C.) 0.048 0.084 0.120 0.056 0.098 0.140 0.064 0.112 0.16 (H.C.)/(C.C) ratio % w/w 4 7 10 4 7 10 4 7 10 Sodium acetate 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 EDTA Disodium salt 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 Sodium metabisulfite 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 Acetic acid 0.26 0.26 0.26 0.26 0.26 0.26 0.26 0.26 0.26 Results obtained in the stability tests effected at room temperature on the compositions given in preceding Table III. Data herein provided are the average of three determinations. Abbreviations used in the Table Form.= formulation; - Form. rec. = Formulation recovered ( figures in grams ) by emptying the container in a beaker after pressing the valve; - % on the theor. content = percentage by weight of the formulation recovered on the theoretical content; - Mesalazine titre .= titre of mesalazine in the quantity recovered of the formulation; - Residue g. = residual grams of formulation found after opening and emptying the container. Form. I A Form. I B Form. I C Form. II A Form. II B Form. II C Form. III A Form. III B Form. III C TIME ZERO Form. rec. (g.) 60.84 60.96 61.03 60.93 61.10 60.86 60.99 61.03 61.05 % on the theor. content 98.2 98.4 98.5 98.4 98.6 98.2 98.5 98.5 98.6 Mesalazine titre 6.66 6.67 6.67 6.66 6.68 6.67 6.67 6.67 6.67 Residue g. 0.78 0.74 0.80 0.75 0.67 0.77 0.64 0.82 0.72 ONE YEAR Form. rec. (g.) 61.06 60.86 61.13 60.85 60.98 60.94 60.85 61.10 60.88 % on the theor. content 98.6 98.2 98.7 98.2 98.4 98.4 98.2 98.6 98.5 Mesalazine titre 6.66 6.65 6.66 6.67 6.65 6.66 6.65 6.67 6.68 Residue g. 0.70 0.80 0.65 0.78 0.79 0.78 0.89 0.65 0.86 TWO YEARS Form. rec. (g.) 60.87 60.97 60.85 60.99 61.02 60.93 61.14 61.07 60.97 % on the theor. content 98.2 98.4 98.2 98.5 98.5 98.4 98.7 98.6 98.4 Mesalazine titre 6.68 6.67 6.66 6.65 6.67 6.67 6.67 6.67 6.65 Residue g. 0.80 0.75 0.83 0.74 0.78 0.73 0.65 0.67 0.80 Example 1 Preparation of formulation A of Table I. In 4.8 kg of distilled water, in a nitrogen atmosphere, were dissolved g 5 of EDTA and g 41.0 of anhydrous sodium acetate. pH was then adjusted to 4.8 with about 19 ml of glacial acetic acid. 25 g of sodium metabisulphite were then added. The solution was transferred into a reaction vessel that was then hermetically closed. Vacuum was afterwards effected ( 300 - 400 mm Hg ). Under a vigorous stirring were dissolved 60 g of hydroxyethylcellulose ( Natrosol® 250HHR ). The solution was then warmed up to 45°C and at that temperature became of a gel-like consistency. The temperature was then lowered to 25 - 35°C. 333.5 g of mesalazine were added. Vacuum was afterwards set up again and a vigorous stirring started. 5148 g ( volume about 5040 ml ) of a suspension according to formulation A were obtained, that was then divided into 50 packages pressurized with nitrogen gas ( 9 - 10 Atm ) having a diameter of mm 35 and volume of 110 ml. Each container was filled with 60 ml. Example 2 Preparation of a suspension containing ( % w/w ) : mesalazine 6.67 %, 2.2% of thickening agent ( hydroxyethylcellulose ), 0.1% disodium EDTA,. 0.5% sodium metabisulphite, 0.67% sodium acetate. Under a nitrogen atmosphere, in kg 5.7 of distilled water were at first dissolved 6 g of disodium EDTA, 40.35 g of anhydrous sodium acetate, about 17 ml of glacial acetic acid to bring pH to 4.83, and 30 g. of sodium metabisulphite. Under stirring were then added 120 g of hydroxyethylcellulose ( Natrosol® 250HHR ) and the solution was warmed at 50°C under a moderate agitation until a gel was formed, and then transferred into a vessel that was afterwards tightly closed. Vacuum was therein effected and the viscous solution was heated at 50°C under stirring. The mass was slowly cooled and, under agitation, 400.2 g of mesalazine added. The suspension was then milled in a colloid mill and collected into a container under a nitrogen atmosphere. kg 5.01 ( about 4910 ml) of the product were obtained. The assayed titer of the active principle corresponded to the theoretical. One litre of said preparation was divided in 60 ml aliquots into 16 100 ml glass vessels having an inner diameter of 4.6 cm ( external 6 cm ) and height 56 mm, afterwards tightly sealed and stored at 25°C in the dark. After one month three containers were taken out and emptied with caution in separate beakers. It was observed the presence of a solid residue at the bottom. HPLC analysis of the active principle performed on the supernatants evidenced that the titer of mesalazine was of 93.9 % of that found at time zero. Example 3 Preparation of a suspension containing 6.67% ( w/w ) mesalazine, 2% thickening agent ( hydroxyethylcellulose - Natrosol® 250HHR ), 0.25% surface active agent ( Tween® 20), 0.1% disodium EDTA, 0.67% sodium acetate, 0.5% sodium metabisulphite. In 440 g of distilled water were dissolved 1.25 g of Tween® 20, 0.5 g of EDTA disodium salt, 3.36 g of anhydrous sodium acetate. pH was corrected to 4.8 with about 1.4 ml of glacial acetic acid and 2.5 g of sodium metabisulphite added. 10 g of hydroxyethylcellulose and then 33.33 g of the active principle were then admixed and dissolved in the solution with the same procedure described in example 1. At the end distilled water was added to yield 500 g. Aliquots of the freshly prepared suspension were transferred into n. 4 100 ml centrifuging tubes and centrifugation effected at 4000 rpm for 15 minutes. After careful removal of the supernatant a solid residue was found at the bottom of the test tubes. Said residue contained a fairly large amount of mesalazine, as shown by assaying ( HPLC ) the titer of the active principle in the supernatant, found to be 74,35% of that expected on the basis of the quantity used for preparing the suspension. Example 4 Preparation of mesalazine suspensions having colloidal cellulose concentrations w/v of 1; 1.1; 1.2; 1.3; 1.4; 1.5; 1.6; 1.8 and 2.0 % respectively, and thickening agent concentrations, as percentage by weight to the quantity of colloidal cellulose, of 2; 4; 6; 8; 10; 12; 14; 16; 18, 20 and 25% respectively, mesalazine 6,67 % w/v, sodium acetate 0.8% w/v, disodium EDTA 0.1% w/v, sodium metabisulphite 0.5% w/v. Each suspension was prepared in a standard quantity of 1 litre with the following procedure. At first 9 different suspensions of colloidal cellulose (Avicel® RC 591 ) were prepared by using a 10 litre reaction vessel, wherein were transferred each time aliquots of 7.5 liters of water to which were separately added, in the order, 125 g, 137.5 g, 150 g, 162.5 g, 175 g, 187.5 g, 200 g, 225 g, 250 g of the above compound . Stirring was continued until a colloidal solution was obtained. On the basis of the above colloidal cellulose quantities in a 600 ml aliquot of each of said nine suspensions were hence contained, respectively, 10 g, 11 g, 12 g, 13 g, 14 g, 15 g, 16 g, 18 g e 20 g of the compound. Separately, in 300 ml aliquots of distilled water a quantity of hydroxyethylcellulose (Natrosol® 250HHR ) was dissolved in order to yield the weight ratios to colloidal cellulose reported in the title of this example. When a clear solution of the thickener had been formed, mixing was effected with the corresponding 600 ml aliquot containing the quantity of colloidal cellulose on which that of hydroxyethylcellulose has been calculated. To each of the solutions thus obtained were then added 8 g of anhydrous sodium acetate and 2 - 3 ml of glacial acetic acid . The final pH was of about 4.8. 1 of EDTA disodium salt and 5 g of sodium metabisulphite were then added. In a nitrogen atmosphere and under stirring each solution was admixed with 66.7 g of 5-ASA, continuing afterwards stirring until an homogeneous dispersion was obtained. The suspension was then brought to the volume of 1 litre with distilled water. Each suspension was then divided into two parts. With one half were filled 100 ml glass containers having the dimensions set forth in Example 2. With the other half were filled syringes ( syringes Steringa ® , Artsana, Casnate Como ) having the characteristics being formerly reported in the disclosure. The glass containers and syringes filled with the same preparation were divided in 4 groups which were then stored, respectively, at 3°C, room temperature, 30°C e 40°C for one month. At the end the glass containers were turned carefully upside down in order to ascertain whether a precipitate had been eventually collected at the bottom, and it was found out that a solid residue was present in all of those samples having a colloidal cellulose content less than 1.2% w/v. The precipitate was furthermore particularly abundant in those samples stored at 30°C and 40°C. The viscosities of the suspensions from which no precipitate had been separatedwere afterwards checked . A preliminary qualitative test was carried out by emptying the filled syringes after removal of the needle. At the same time absolute viscosity determinations were performed on some of the samples. Both assays had been formerly here above described. The formulations having a quantity of colloidal cellulose higher than 1.6% were quite viscous and in the here above qualitative reported test of emptying the filled syringes did not provide the results awaited ( see here above in the description). On the other side the formulation containing a quantity of the thickening agent, given in ratio by weight to colloidal cellulose, higher than the upper limit of 20% i.e. 25%, showed a marked thixotropy since they recovered very early high viscosity values. This was considered an undesirable feature for the reasons stated already in the description. Furthermore it was also observed that wherein the ratio of the thickening agent to colloidal cellulose was below 4% the composition was no more stable. Example 5 Preparation of nine mesalazine suspensions containing colloidal cellulose in quantities respectively of 1.2; 1.4; 1.6; % w/v calculated on the overall composition, a thickening agent ( hydroxyethylcellulose ) in quantities respectively of 4 ; 7 and 10 % w/w calculated on each of the here above percentages w/v of colloidal cellulose, mesalazine 6.67 %, sodium acetate 0.8%, disodium EDTA 0.1%, sodium metabisulphite 0.5%. Each suspension was prepared in a standard quantity of 1 litre with the following procedure. Under stirring in 600 ml separate aliquots of distilled water was suspended colloidal cellulose (Avicel® RC 591 ) in the quantities, respectively, of 12 g, 14 g, and 16 g. Stirring was continued until a colloidal suspension was obtained. For each of the above concentrations were prepared n. 3 600 ml samples. Separately were prepared 300 ml aqueous solutions of hydroxyethylcellulose ( Natrosol® 250HHR ) containing respectively the following quantities of the compound : A ) 480 mg, 840 mg and 1200 mg . B ) 560, 980 and 1400 mg. C ) 640, 1120, 1600 mg. The solutions of group A were separately admixed with 600 ml of the suspension containing 1.2% w/v colloidal cellulose. Those of group B were separately admixed with 600 ml of the suspension containing 1.4% w/v colloidal cellulose. Those of group C were separately admixed with 600 ml of the suspension containing 1.6 % w/v colloidal cellulose. To the suspensions thus obtained were then added 8 g of anhydrous sodium acetate and 2 - 3 ml of glacial acetic acid . The final pH was of about 4.8. 1 of EDTA disodium salt and 5 g of sodium metabisulphite were then added. In a nitrogen atmosphere and under stirring each solution was admixed with 66.7 g of 5-ASA, continuing afterwards stirring until an homogeneous dispersion was obtained, which was then brought to the volume of 1 I with distilled water. Density determinations made by the aid of a 25 ml picnometer at the ambient temperature afforded the average value of 1.03. Said suspensions were then transferred into pressurized packagings, each containing 60 ml of the formulations, The containers were the same as those described in example 1. Example 6 Preparation of an industrial batch of the formulation of the invention having the following composition referred to 60 ml of the final product ( percentages, wherein not otherwise indicated, are in w/v ) : Mesalazine 6.67 %, colloidal cellulose 1.4 %, hydroxyethylcellulose 7% w/w to colloidal cellulose, sodium acetate trihydrate 1.08%, sodium metabisulfite 0.5%, disodium EDTA 0.1 %, glacial acetic acid enough to pH 4.8. In a 600 I stainless steel reaction vessel 5.880 Kg of colloidal cellulose (Avicel® RC 591) were suspended in 252 I of distilled water under vigorous agitation. The process was eased by operating concomitantly a colloid mill. On a further aliquot of 126 I of warm water at 45°C, in a 200 litre stainless steel vessel, were dissolved under stirring Kg 0.411 of hydroxyethylcellulose. The solution was then cooled to room temperature and added to the cellulose suspension under thorough mixing. In the order, to the resulting colloidal solution, were then added 0.420 kg of EDTA disodium salt, 4.522 Kg of sodium acetate trihydrate, 2.100 Kg of sodium metabisulfite. The vessel was then hermetically closed and vacuum was therein made ( 200 mm Hg ). Kg 14 of mesalazine were then added under stirring. About 1 I of glacial acetic acid was then added and the solution brought to the final volume of 420 I with distilled water. With the above quantity could be prepared 7000 pressure packings containing 60 ml each of the suspension of the invention. Example 7 Pharmacological clinical trial with the new compositions and assessment of the distance travelled in the large intestine. For said clinical trial the active principle 5-ASA had been radioactive labelled with 100 MegaBequerel of colloidal 99m Tc sulfide ( Technetium isotope 99 sulfide ). Since this salt has an half-life of 6 hours only, the compositions were radioactively labelled within 2 hours from their administration. To the trial were admitted twelve patients aged between 18 and 70 years, of both sexes. Admission criteria were as it follows : Distal ulcerative cholitis progressed up to at least 20 cm from the anus but not above the splenic flexure ( established by colonoscopy at least 7 days before the beginning of the trial ), low or moderate inflammation, five or more diarrhea episodes / day with blood and mucous in at least one discharge, abdominal pain, tachycardia, anemia, anorexia and vomiting. In n. 6 out of 12 patients the disease was ascertained to occur in the sigmoid-rectum portion of the intestine and in the others in the colon. 48 hours before the start of the trial therapy with sulfasalazine or other active principle related to 5-ASA was interrupted. Each patient was administered rectally with 60 ml of the composition according to example 8. A scintigraphic analysis was then carried out on the abdomen of the patients, kept in a prone position, respectively at 5, 30, 60, 120, 180 and 240 minutes from enema administration. The results obtained evidenced that in 11 out of 12 patients ( 92% ) the enema went above the sigmoid colon and in 6 patients arrived up to the transverse colon. In said latter group about 19% of the total radioactivity was still found in the transverse colon. The average time employed by the formulation to get to the point farthest from the rectum was of 4 hours ( hours for 6 patients and 6 for the other half ). Example 8 ( Composition % w/v) mesalazine 6.67% colloidal cellulose 1.40% hydroxyethylcellulose 0.07% sodium acetate trihydrate 1.08% sodium metabisulphite 0.50% EDTA disodium salt 0.10% glacial acetic acid enough to pH 4.6 water enough to ml 100 Example 9 ( Composition % w/v ) mesalazine 3.33% colloidal cellulose 1.20% carboxypolymethylene 0.20% sodium acetate trihydrate 1.08% sodium metabisulphite 0.50% EDTA disodium salt 0.10% glacial acetic acid enough to pH 4.9 water enough to ml 100 Example 10 ( Composition % w/v ) mesalazine 6.67% colloidal cellulose 1.60% sodium carboxymethylcellulose 0.16% sodium acetate trihydrate 1.08% sodium metabisulphite 0.50% EDTA disodium salt 0,10% glacial acetic acid enough to pH 5.1 water enough to ml 100 Example 11 ( Composition % w/v ) mesalazine 3.33% colloidal cellulose 1.30% xantan gum 0.26% sodium acetate trihydrate 1.08% sodium metabisulphite 0.50% EDTA disodium salt 0.10% glacial acetic acid enough to pH 4.5 water enough to ml 100 Example 12 ( Composition % w/v) mesalazine 6.67% colloidal cellulose 1.50% Hydroxypropylmethylcellulose 0.06% sodium acetate trihydrate 1.08% sodium metabisulphite 0.50% EDTA disodium 0.10% glacial acetic acid enough to pH 4.8 water enough to ml 100 Example 13 ( Composition % w/v ) mesalazine 3.33% colloidal cellulose 1.30% methylcellulose 0.10% sodium acetate trihydrate 1.08% sodium acetate trihydrate 0.50% EDTA disodium 0.10% glacial acetic acid enough to pH 4.7 water enough to ml 100 Example 14 ( Composition % w/v ) mesalazine 3.33% colloidal cellulose 1.40% xantan gum 0.21% sodium acetate trihydrate 1.08% sodium metabisulphite 0.50% EDTA disodium salt 0.1% glacial acetic acid enough to pH 4.6 water enough to ml 60 Example 15 ( Composition % w/v ) mesalazine 6.67% colloidal cellulose 1.60% carboxypolymethylene 0.32% sodium acetate trihydrate 1.08% sodium metabisulphite 0.50% EDTA disodium salt 0.10% glacial acetic acid enough to pH 4.8 water enough to ml 100 Example 16 Description of a pressure packaging containing inside an aluminium bag filled with the suspension of the invention. Internal volume of the packaging : 110 ml ( external diameter : 35 mm ). Gas pressure inside ( nitrogen) : 9 atm. The bag made of aluminium thin foil is placed around the vertical axis of the actuator, it occupies about 60% of the total inner volume of the container and is filled with 60 ml of the suspension of the invention. The outer side of the aluminium foil is covered with propylene, the inner with polyethylenetereflalate.

Claims: Pharmaceutical composition in the form of an aqueous thixotropic suspension containing mesalazine and comprising usual excipients such as sequestrants, bacteriostatic agents, antioxidants and additionally buffering agents or inorganic acids, characterized in that it contains colloidal cellulose in a quantity from 1.2 to 1.6% w/v and one or more hydrophilic thickening agent in a percentage by weight ratio to colloidal cellulose of between 4 and 20%, or 0.048 - 0.32 % by weight referred to the solution volume, the pH of the composition being comprised between 4.5 and 5.1. Pharmaceutical composition according to Claim 1 characterized in that the percentage by weight ratio of the hydrophilic thickening agent to colloidal cellulose is of between 4 and 10%. Pharmaceutical composition according to the preceding Claims characterized in that the percentage of colloidal cellulose is of 1.4% w/w and that the percentage by weight ratio of the hydrophilic thickening agent to colloidal cellulose is of 6 or 7%. Pharmaceutical composition according to Claims 1-3 characterized in that the hydrophilic thickening agent is chosen in the group consisting of carboxypolymethylene, sodium carboxymethylcellulose, hydroxyethylcellulose, xantan gum, hydroxypropylmethylcellulose, methylcellulose, carrageenan. Pharmaceutical composition according to the preceding Claims characterized in that the hydrophilic thickening agent is hydroxyethylcellulose. Pharmaceutical composition according to the preceding Claims being contained in pressure containers having as propellant an inert gas. Pharmaceutical composition according to the preceding Claim being contained in an hermetically sealed bag placed inside the pressurized container. Process for manufacturing the pharmaceutical composition according to Claim 1 characterized in that it comprises the following steps : a. In two separate aliquots of distilled water, being respectively 60% and 30% v/v of the total volume of distilled water to be used, are dissolved colloidal cellulose and the thickening agent. b. Said two aliquots are admixed and added of the other excipients of the composition. c. The active principle is added to the suspension under vacuum and thorough stirring. d. The suspension is afterwards brought to the final volume by adding distilled water.

Inventors: FAROLFI GIANCARLO, FERRO LAURA, LATTUADA FRANCO, FAROLFI, GIANCARLO, FERRO, LAURA, LATTUADA, FRANCO
Applicants: CRINOS INDUSTRIA FARMACO, CRINOS INDUSTRIA FARMACOBIOLOGICA S.P.A.
Application year: 1996
Main classification: A61K31
IPC codes: A61K9, A61K47, A61P1, A61K31