PROLAMINE COATINGS FOR TASTE-MASKING ORALLY-ADMINISTRABLE MEDICAMENTS

Abstract: Prolamine fractions of grain proteins, applied in weight ratios of 5 to 100 % relative to the active agent being coated, effectively prevent the partitioning of water-soluble or water-insoluble drugs at neutral pH's in the mouth and thereby mask the taste of orally-administered drugs, which normally have a bitter taste, without sacrificing bioavailability. Zein, gliadin or a mixture thereof, particularly in combination with between 2.5 and 15 % of water-insoluble vegetable source oil or wax capable of plasticizing the prolamine fraction, when applied to particles, granules, tablets or other forms of drugs or nutritionals, to an effective thickness of about 1 to about 35 micrometers, in order to encapsulate and prevent release of an orally-administered pharmaceutical or nutritional in a suspension or chewable dosage form until such medicament reaches the stomach.

Description: PROLAMINE COATTNGS FOR TASTE-MASKING ORALLY-ADMINISTRABLE MEDICAMENTS TECHNICAL FIELD The present invention relates to oral formulations which effectively mask the undesirable tastes of drugs, such as antibiotics or benzodiazepines, and nutritionals, such as dietary fiber or amino acid supplements, and other similar pharmaceuticals or nutritionals with bitter or otherwise undesirable tastes. In particular, the invention relates to taste-masked medicaments capable of being chewed or swallowed without producing a bitter taste in the mourn. BACKGROUND OF THE INVENTION Oral administration of pharmaceuticals and nutritionals is one of the most popular methods of delivery of such beneficial agents. Chewable or suspension dosage forms are the preferred route of such oral administration for both children and adults who have difficulty swallowing capsules or tablets, with palatability being an extremely important factor in formulating these dosage forms in order to maximize the likelihood that the recipient will take the pharmaceutical or nutritional. Because of the strong, unpleasant taste of many medicaments, flavorings, either alone or in combination with sweeteners and other additives, have been employed to improve taste and palatabilty. The formulation of a pleasant-tasting and palatable product through the sole use of flavorings, sweeteners and additives, however, has been unsuccessful in many medicaments which have a particularly bitter taste, such as the macrolide family of antibiotics, in particular ery thromycin and clarithromycin. Attempts have been made to formulate these antibiotics into suspension dosage forms or into taste-masked chewable tablets using known coating or encapsulation processes with very limited success. Tsutomu, in Japanese Patent Application 45-12759, published November 1, 1967, claims pharmaceutical compositions consisting of zein and hydroxypropylmethylcellulose (HPMC) in coating tablets to mask taste and odor. The application employs the high molecular weight polymeric HMPC component (exemplified at levels of 10% and above) for its film-forming properties, in a coating used to prevent the disintegration of Vitamin C as measured by temperature and time. Pescetti, in U.S. Patent 3,939,259, issued Feb. 17, 1976, employed prolamine from corn grain protein (i.e., zein), with approximately an equal level of shellac and a lesser amount of ethylcellulose, to coat digitoxin particles, but did so to achieve a sustained, -release effect. Since the incorporation of ethylcellulose may interfere with absorption of the active agent in a timely manner, its incorporation into the present invention for an imediatately-available medicament would be unsuitable. Cea, in U.S. Patent 4,384,004, issued on May 17, 1983, discloses the encapsulation of the artificial sweetener, L-aspartyl-L-phenylalanine methyl ester (APM), with additional coating materials, which may include zein, for increasing shelf life stability. Li comparison with these known formulations, the present invention provides a taste-masked product in a chewable or nonchewable dosage form or suspension, with immediate bioavailability. Additionally, the taste-masking ability of the present invention is due solely to the prolamine firaction of grain, with only minor levels of a low-to-moderate molecular weight plasticizer needed to form the film coating. Summary of the Invention The present invention is directed to an orally-administerable medicament comprising (a) a core-mixture of a pharmaceutically-active agent or nutritional, having a surface and (b) an outer polymeric coating layer comprising a prolamine fraction of grain protein, preferably zein or gliadin or mixtures thereof, and a low-to-moderate weight nσnpolymeric agent for plasticizing said prolamine, preferably a vegetable source water-insoluble oil or wax, wherein the ratio of prolamine to plasticizing agent Ϊs from40:l to 20:3. The present invention further relates to a medicament wherein the ratio of t he pharmaceutically-effective agent or nutritional to the prolamine fraction is 20:1 to 1:1, and the outer layer is from about 1 to about 35 micrometers thick. In particular, the invention comprises taste-masked medicaments capable of being incorporated into a suspension or chewable dosage form without producing a bitter taste. Brief Description of the Drawings. Figure 1 is a graph of the plasma concentration of clarithromycin versus time of both the zein-coated clarithromycin suspension and the clarithromycin tablet reference, administered at 125 mg of clarithromycin activity per dog. Figure 2 is is a graph of the bitterness (on a scale of 0 to 3, where 0 represents no bitterness and a 3 represents a strong bitterness) observed for a clarithromycin concentration in solution. Figure 3 is a graph of the bitterness observed for the formulation of zein- coated clarithromycin particles in an aqueous environment for both an initially- prepared suspension (Day 0) and one which was prepared and allowed to stand for 7 days, as a function of time after tasting. Detailed Description of the Invention: The present invention relates to the use of an outer polymeric coating layer to effectively taste-mask pharmaceutically-active agents or nutritionals which have bitter or otherwise undesirable tastes. The formulations of the present invention comprise (a) a core of a pharmaceutically-active agent or nutritional, as well as diluents, fillers or other inactive ingredients necessary for the formation of the pharmaceutical core, and (b) an outer polymeric coating layer comprising a prolamine fraction of grain proteins and a low-to-moderate molecular weight plasticizing agent for said prolamine. The prolamine fraction is purified from corn or wheat and includes zein or gliadin or mixtures thereof, but preferably is zein (the prolamine fraction of com) which has been purified to between 86-96%, most preferentially, 92-96%. Additionally, the prolamines present in the preferred coating formulation will be present in a solution consisting of 90% food grade ethanol and 10% distilled water at a preferred level of between 5% and 20% prolamine. The plasticizing agent which is preferentially present on a weight basis between 2.5% and 25% relative to the prolamine fraction, is a water-insoluble vegetable source oil or wax, and includes, but is not limited to, fatty acids of chain lengths six to twenty-two (both saturated and unsaturated carbon chains are equally suitable), nonionic cellulosic polymers (e.g., hydroxypropyl cellulose and hydroxyethyl cellulose), and polyvinylpyrrolidone of molecular weight range 30,000 to 400,000 daltons. Most preferred plasticizers are fatty acids of chain lengths six-to- eighteen which are present on a weight basis of between 2.5 and 15 %. The optimum thickness of the coating material is between about 1 and about 35 microns to the core of the pharmaceutically-active agent or nutritional. The preferred level of coating consists of from about 5 % to about 100 % of applied film polymeric coating, where the major constituent is the prolamine fraction of grain protein (with the percent representing the weight of film coating relative to the initial weight of the core of the medicament). The most preferred level of coating is between 45 to 75 % weight of coating to weight of the medicament core. The preparation of the formulation may be accomplished by a variety of coating techniques known in the art, including fluidized bed coating, coacervation (Le., microencapsulation), or a combination thereof as disclosed by Cea et al. in U.S. Patent 4,384,004. Preferably.wet granulation techniques may be employed to form the medicament core, and fluidized bed coating, with a Wurster column insert may preferentially be employed to apply the coating, as described by Mehtaet al. in U.S. Patent 4800087. The preferred method for preparing the pharmaceutically-active core is to co¬ mix the active agent with a portion of inactive binder consisting of TM polyvinylpyrrolidone (Povidoiie made by International Specialty Chemicals Corp.) of a molecular weight range of 30,000 to 400,000 in a weight to weight basis of 5 % to 65 % of the active ingredient Alternative granulating agents capable of assisting in the formation of a particle containing the active ingredient include, hydroxypropylcellulose (Klucel TM , Hercules Corporation), hydroxypropylmethyl TM cellulose, (Methocel , Dow Chemical Corp.), Pregelatinized Starch, (Colorcon, Inc.) or any other material suitable for use as a binding agent for the formation of particles capable of being utilized as pharmaceutically active cores. After blending, a sufficient portion of water or food grade ethanol is added to wet mass the mixture into a wet granulation. This material may be either oven-dried under mild heat or dried in a fluidized bed air-drying system, which is capable of performing the task in a more efficient, less time-consuming fashion. The particles are then dried to a specified level of dryness (based on weight loss measurements) and milled to produce a small particle size range. These particles may then be sieved to collect the fraction of particles of a particular size range for subsequent coating. Alternate methods for preparing particles are equally useful at creating particles of a suitable size range. A wide range of medicaments are suitable for formulation in the present invention. Such medicaments include antibiotics, preferably macrolide antibiotics, and other antibacterial agents, analgesics, antihistamines, decongestants, anti-inflammatory agents, hypnotics, sedatives, tranquilizers, vitamins, enzymes, nutritional supplements, hormones and the like. Those with an especially bitter taste, such as macrolide antibiotics, specifically erythromycin and clarithromycin, are particularly suited for the present invention. The formulation of the present invention may be incorporated into a variety of pharmaceutical and nutritional products, including pharmaceutical suspensions, pediatric infant formulas, and nutritional supplements. Exam le 1 A. Preparation of Clarithromycin : Polyvinylpyrrolidone Particles To a pharmaceutically-active core consisting of clarithromycin, 90%, and polyvinylpyrrolidone (Povidone, K-30, ISP Corp.), 10%, a sufficient amount of food grade ethanol was added with mixing to form a wet mass. The wet granulation was then dried in an oven (between 50° and 60°C) until the loss on drying (LOD) was less than 1%. These particles were.,then ground to a smaller size and the fraction of particles between 177 and 420 microns collected (40-80 mesh fraction). B. Preparation of Zein-Coated Clarithromycin : Polyvinylpyrrolidone Particles. To 4 kg of the Clarithromycin : polyvinylpyrrolidone particles, prepared as described above, was applied 2.8 kg of solids contained in a coating formulation consisting of zein (93%) and medium chain triglycerides (7%). This coating formula was dispersed in a mixture of 90% food grade ethanol and 10% distilled water to a level of 10.75% solids (prolamine fraction and medium-chain triglycerides), in this cosolvent mixture. The coating was performed in a Glatt GPCG-5 bottom spray particle coater with a fluidized bed and a Wurster column. Inlet temperature was maintained between 39° and 45°C, with the exhaust temperature between 26° and 29°C, and the atomization pressure on the spray nozzle was maintained between a range of 26 and 30 pounds per square inch. The flow rate of application of coating liquid to the particles was maintained in the range of 10 to 15 mL per minute. Example Dissolution of Zein-Coated Clarithromycin : Polyvinylpyrτolidone Particles as a Function of pH. The zein-coated Clarithromycin : polyvinylpyrrolidone particles, prepared as described in Example 1 A,were tested using a dissolution apparatus to evaluate the percent of active ingredient released into a 900 mL dissolution bath of pH-buffered solution over a two hour period. A dose of 125 mg of clarithromycin activity was was used as a representative dose and dissolution was tested at pH 2.0, 5.0, and 6.8. Samples were withdrawn at 30, 60, 90 and 120 minutes. The results, as shown by Table I, below, indicate no active drug was released at pH 6.8. Rapid release of the active drug was observed atpH 2.0. Table 1 - l hr cin P l vin rr n 1. Particles coated with 70% weight coating to weight of particle. 2. Average (+S.D.), n=3. 3. No detectable response. Example 3 Release of Zein-Coated Clarithromycin : Polyvinylpyrrolidone Particles as a Function of Time. To a solution in which sodium bicarbonate (50 mg/5 cc) was dissolved, 125 mg/5 cc of clarithromycin activity (accounting for potency of the active agent and the particles), was added, shaken and observed for release of active agent as a function of time. Samples were withdrawn, filtered, and measured at 0,4, 24, 72, and 196 hours. The samples were filtered to remove the suspended particles and the clear filtrate was analyzed for clarithromycin content The results, as shown in Table 2, below, indicate that very low levels of active drug are released over prolonged periods of time. Table 2 Release of Zein-Coated Clarithromycin : Polyvinylpyrrolidone Particles as a Function of Time. Time (hours) Concentration (mcg/ml) Percent % 0.08 0.24 0.40 0.47 0.41 Example 4 Formulation of Zein-Coated Clarithromycin Zein-coated clarithromycin , comprising 70% coating was formulated as follows: Ingredient Amount per dose (5cc) Coated clarithromycin 260. mg (125 mg activity) Sucrose 3000. mg Xanthan gum 7.5 mg Silica Gel 10.0 mg Potassium Sorbate 20.0 mg Bubble Gum Flavor 14.0 mg Sodium Bicarbonate 50.0 mg Totals: 3361.5 mg 5 mL final volume Example 5 Bioavailability of Zein-Coated Clarithromycin The bioavailability of zein-coated clarithromycin, formulated as described in Example 4, was conducted in a beagle dog model using an single cross-over design. The study compared single dose immediate release tablets containing 125 mg of clarithromycin activity to the microcapsules of clarithromycin prepared as described in Example 1, above, and formulated as described in Example 4, above. The release of clarithromycin was demonstrated by a cross over comparison of the bioavailability of the formula in a beagle dog model compared to a tabletreference containing same. The cross over design allowed the same dogs to receive both the zein-coated clarithromycin suspension as well as the clarithromycin reference tablet of the same dose (125 mg clarithromycin activity). The results, illustrated in Figure 1, demonstrate that the zein-coated clarithromycin suspension did not release the clarithromycin in the suspension (as shown by a representative suspension in Example 3, Table 2), but rapidly released the active drug in the gastrointestinal tract of the dog for equivalent absorption to that of the reference tablet Example 6 Flavor Evaluation of Zein-Coated Clarithromycin Comparative flavor evaluation noting characteristics of bitterness of the particle-coated clarithromycin and clarithromycin in solution was conducted. The formulation used was that described in Example 4, and was compared with clarithromycin in solution as a reference standard for the level of bitterness observed for the samples. The study was conducted using trained flavor specialists who standardize their palate with the use of references which were, in this case, the solutions of clarithromycin. The study consists of swirling a dose of the material, solution or suspended formulation, in the mouth and then ranking bitterness, relative to standards, as a function of time after tasting it. The period of time after tasting is evaluated in the event that particles remain or get lodged in the oral cavity before being removed by salivary secretions. The dose response for the clarithromycin in solution can be seen in Figure 2 and the corresponding level of response for the suspension is shown in Figure 3, as a function of time after tasting, to demonstrate the lack of bitterness of this formulation. Figure 3 thus shows that levels of free clarithromycin available for interaction with taste buds are below 15 ppm even after 7 days in suspension,thus demonstrating the taste-masking ability of the zein coating for an example of a very bitter pharmaceutically-active agent Although the invention has been exemplified in specific modifications, the details are not to be construed as limitations, for it will be apparent that various equivalents, changes and modifications may be employed without departing from the spirit and scope thereof, it being understood that such equivalent embodiments are intended to be included therein.

Claims: CLAIMS What is claimed is: 1. An orally-administered medicament comprising (a) a core of a pharmaceutically-active agent or nutritional having a surface, and (b) overlaying said surface, an outer polymeric coating comprising a prolamine fraction of grain proteins and a low-to-moderate molecular weight plasticizing agent for said prolamine, wherein the ratio of prolamine to plasticizing agent is from about 40:1 to about 20:3. 2. A medicament according to Claim 1, wherein the Iow-to-moderate weight plasticizing agent is a water-insoluble vegetable source oil or wax. 3. A medicament according to Qaim 1, wherein the ratio of the phaπnaceutically- effective agent or nutritional to the outer polymeric coating is from 20: 1 to 1 : 1 and the outer polymeric coating is from about 1 to about 35 micrometers thick. 4. A medicament according to Claim 1, wherein the prolamine fraction is zein or gliadin, or a mixture thereof, and said prolamine fraction has been purified to 88- 96%. 5. A medicament according to Claim 1, which is in the form of a chewable tablet or microcapsular suspension. 6 A medicament according to Claim 1 , wherein said pharmaceutically-active agent or nutritional comprises an antibiotic, vitamin, dietary fiber, analgesic, nutritional, enzyme, or hormone. 7. A medicament according to Claim 6, wherein said phaπnaceutically-active agent or nutritional is a macrolide antibiotic. 8. A medicament according to Claim 7 , wherein said macrolide antibiotic is clarithromycin or erythromycin.

Inventors: MAZER TERRENCE B, MEYER GLENN A, MAZER, TERRENCE, B., MEYER, GLENN, A.
Applicants: ABBOTT LAB, ABBOTT LABORATORIES
Application year: 1992
Main classification: A61K9
IPC codes: A61K9