Abstract:
A pharmaceutical mixture with controlled release of actice substance which includes masking of bad taste and stability increasing of active substance characterized in that an encapsulated active substance is combined with a substance controlling the release of active substance from the encapsulation and method for preparing said mixture.

Description:
This application is a continuation of Ser. No. 500,618, filed on June 3, 1983 and now abandoned and also this application is a continuation-in-part of copending U.S. patent application Ser. No. 668,168, filed Mar. 11, 1984, now issued as U.S. Pat. No. 4,656,027, which is a continuation-in-part of U.S. patent application Ser. No. 383,148 filed May 28, 1982 and now abandoned. 
    
    
     DESCRIPTION 
     1. Technical Field 
     The present invention is concerned with an oral pharmaceutical preparation containing an encapsulated pharmaceutically active substance. More specifically the preparation is a dry powder for mixture or said dry powder dissolved in an aqueous solution. 
     The object of the invention is to provide a preparation wherein the dissolution of the active substance from the encapsulation is controlled. 
     2. Background Art 
     Among alternative forms of orally administering pharmaceutically active substances the use of a solution or a suspension of the active principle in an aqueous solution is a form often seen in pediatric use. This preparation is called a mixture. The dry powder including the active principle and adjuvants which is to be dissolved or suspended is called dry powder for mixture. 
     The preparation is stored as a dry powder. Before administration the dry powder is dissolved or suspended in an aqueous solution giving rise to a liquid formulation for oral administration--a mixture. Alternatively the mixture can be prepared in the factory and stored at least for two years prior to administration. Pharmaceutically active substances for use in mixtures have been encapsulated either to mask bad taste or to control the release in the body. 
     Hitherto medicines have been coated with polymers or with polymers in combination with plasticizers to control drug release (microencapsulation). Applied on granulates of a drug it retards the rate of dissolution. 
     The main way to control drug dissolution from microcapsules is the amount of polymer applied, in order to obtain the expected plasma profile of the drug. This can also be obtained by adding water soluble substances to the coat during the coating process. 
     DISCLOSURE OF THE INVENTION 
     The present invention provides a mixture, wherein bad taste of the drug is masked and/or it provides a mixture with retarded dissolution to obtain slow release effect. 
     The mixture is obtained either by suspending the dry powder in an aqueous solution or by suspending the microcapsules in a solution of the release controlling substance. 
     The drug release from the microcapsules within the mixture, here called leakage, is very low, but in the body the drug is released from the microcapsules and available for absorption. 
     This invention also provides for increased drug stability in the mixture. 
     This result is obtained by adding to the encapsulated active substance and customary adjuvants a release-controlling substance (sink). 
     As sink can be used a carbohydrate or a carbohydrate-related compound, for instance a poly- or a oligosaccharide such as dextrane; a disaccharide such as saccharose, maltose or lactose, a monosaccharide such as glucose, fructose, galactose, mannose or xylitol; a carbohydrate-related compound such as mannitol, sorbitol, glycerol, glycol, a glycoside of a monosaccharide or a substance derived from ethyleneglycol for instance polyethyleneglycol (trade names Carbowaxes: and Carbopoles®). 
     As sink can one or a mixture of two or more of the mentioned substances be used. 
     The amount of sink should be between 40% and 99% (weight/weight), preferably 60-75% (weight/weight) of the entire preparation, that is of the ready to use suspension for oral administration (the mixture). 
     An alternative to adding the release-controlling substance to the encapsulated drug is to encapsulate the release-controlling substance together with the drug within the encapsulating shell. 
     Sugars that can be used according to the invention are among others sucrose, glucose, fructose and sorbitol. 
     As pharmaceutically active substance any drug can be used, for instance anyone of the following: 
     
         __________________________________________________________________________Chemotherapeutics     bacampicillin, ampicillin, flucloxacillin, tetracyc-     line, dicloxacillin, chloramphenicol, gentamicin,     erythromycin, lincomycin, rifampicin, sulphadiazine,     sulphamethoxypyridazine, griseofulvine, nitro-     furantoineAdrenergis     ephedrine, terbutaline, theophylline, enprophyllineand beta-receptor-stimulatorsExpectorants     Ethylmorphine, dextromethorphan, noscapine, bromhexineand coughdepressantsHeartglucosides     Digitoxine, digoxin, dispyramide, procainide, tocain-and       ide, alprenolol, atenolol, metoprolol, pindolol,antiarythmics     propranololBlood pressure     betanidine, clonidine, guanetidine, methyldopa,depressants     reserpine trimetaphane, hydrolazine, bendrop-     phlumetiazide, furosemide, chlorotiazideAntihistamines     brompheniramine, chlorcyclizine, chlorpheniramine,     diphenhydramine, prometazinePeroral   carbutamide, chlorpropamide, tolazamide, tolbutamideantidiabetesSedatives hexobarbital, pentobarbital, phenobarbital, mepro-Hypnotics bamate, chlordiazepoxide, diazepam, flunitrazepam,Antidepressants     nitrazepam, oxazepam, chlormethiazol, chlor-     promazine, fluphenazine, perphenazine, prochlor-     perazin, haloperidol, lithium, alaproclate,     zimeldine, amitryptiline, imipramine, nortriptylineAntiepileptics     phenytoine, ethotoin, ethosuximide, carbamazepineAnalgetics     codeine, morphine, pentazocine, petidine, dextro-Anesthetics     propoxyphene, methadone, acetylsalicylic acid,     diflunisal, phenazone, phenylbutazon, acetamino-     phene, indometazine, naproxen, piroxicam, lidocaine,     etidocaineOthers    cimetidine, quinidine, dicoumarine, warfarine,     potassium chloride, chloroquine__________________________________________________________________________ 
    
     The preferred drug is bacampicillin hydrochloride (1&#39;-ethoxycarbonyloxyethyl 6-[D(-)-2-amino-2-phenylacetamido]-penicillanate hydrochloride), other epimeric forms and the racemic form of bacampicillin hydrochloride. 
     Other preferred drugs are theophylline, enprophylline and erythromycine. 
     The drugs mentioned above are used in neutral or salt form. 
     The following salts of the drugs mentioned above can be used: 
     Acetate, benzenesulfonate, benzoate, bicarbonate, bitartrate, bromide, calcium edetate, camsylate, carbonate, chloride, citrate, dihydochloride, edetate, edisylate, estolate, esylate, fumarate, gluceptate, gluconate, glutamate, clycollylarsanilate, hexylresorcinate, hydrabamine, hydrobromide, hydrochloride, hydroxynaphthoate, iodide, isethionate, lactate, lactobionate, malate, maleate, mandelate, mesylate, methylbromide, methylnitrate, methylsulfate, mucate, napsylate, nitrate, pamoate (embonate), pantothenate, phosphate/diphosphate, polygalacturonate, salicylate, stearate, subacetate, succinate, sulphate, tannate, tartrate, teoclate, triethiodide. 
     Also the further cationic salts can be used. Suitable cationic salts include the alkali metal, e.g. sodium and potassium, and ammonium salts and salts of amines known in the art to be pharmaceutically acceptable, e.g. glycine, ethylene diamine, choline, diethanolamine, triethanolamine, octadecylamine, diethylamine, triethylamine, 1-amino-2-propanol-2-amino-2-(hydroxymethyl)propane-1,3-diol and 1-(3,4-dihydroxyphenyl)-2-isopropylaminoethanol. 
     The encapsulation of the drug can be achieved in the form of microcapsules, but the encapsulation is not restricted to the micro size. 
     COATING MATERIAL 
     Polymers: 
     Synthetic polymers of polyvinyl type, e.g. polyvinylchloride, polyvinylacetate, polyvinylalcohol 
     Polyethylene type, e.g. polyethylene, polystyrene 
     Polymers of acrylic acid or acrylic acid ester type, e.g. methylmetacrylate or copolymers of acrylic monomers 
     Biopolymers or modified biopolymers of cellulose, e.g. ethylcellulose, cellulose acetate phtalate. 
     The polymer can be water insoluble, acid soluble or alkaline soluble and mixed with plastisizer or other filler and water soluble modified biopolymer, e.g. hydroxy propyl cellulose. 
     Also fats and oils, wax, higher fatty acids, higher alcohols or polyhydric alcohols can be used as such or in combination. 
     In one embodiment of the invention bacampicillin hydrochloride (BAPC) is encapsulated in an insoluble, microporous polymer, such as ethyl cellulose and sucrose is used as sink to make a dry powder for mixture, which is then dissolved in water to make a mixture. 
     In another embodiment of the invention BAPC is encapsulated in a polymer soluble in acid, such as Eudragit® E 100 and sucrose is used as sink to make a dry powder for mixture, which is then dissolved in water to make a mixture. 
     In a further embodiment of the invention theophylline is microencapsulated in a shell of ethyl cellulose and sorbitol is used as sink to make a dry powder for mixture, which is then dissolved in water to make a mixture. 
     In a further embodiment of the invention acetylsalicylic acid is encapsulated in a shell of cellulose acetate phtalate and sucrose is used as sink to make a dry powder for mixture, which is then dissolved in water to make a mixture. 
     A release controlling substance is mixed with other constituents and microcapsules of the drug are added to this dry powder and mixed in a conventional blender. This dry powder is then added to bottles in a filling machine. Water is then added, by the customer or at the pharmacy, to dissolve the release controlling substance. 
     Alternatively, a solution of the release controlling substance and other constituents is prepared. The microcapsules of the drug can then be added either to this solution and then filled into bottles ready to use, or the microcapsules of the drug can be filled into a separate container and be added by the customer or the pharmacy to the solution prior to use. 
     BEST MODE OF CARRYING OUT THE INVENTION 
     Leakage Studies 
     Leakage studies were carried out in order to show that the microcapsules will not release any significant amount of the drug into the sink causing bad taste in contact with water, causing degradation or losing its ability to work as controlled release formulation. 
     Microcapsules were added to sink solution according to the invention. The amount of drug which had been released from the microcapsules was analyzed. This is called leakage. The samples were in some instance stored up to 80 days in room temperature. The sink was analyzed spectrophotometrically. The result is given in percent leakage which is the amount of the drug which is in solution divided by the initial amount of microencapsulated drug. 
     In order to demonstrate the effect of the release controlling substance the release studies were also performed in water. Microcapsules were placed in a beaker and water was added. The stirring rate was 30 rpm and the amount of release was calculated as described above. 
    
    
     EXAMPLE 1 
     100 g of dry powder contains 
     
         ______________________________________Bacampicillin hydrochloride                   5.61 gethyl cellulose microcapsules (70% drug)Sodium bicarbonate      0.83 gMannitol                9.35 gSucrose                 83.1 g______________________________________ 
    
     Sodium bicarbonate, mannitol and sucrose were premixed before the microcapsules were added. The final mixing was carried out in a beaker. The mixture contains 46% w/w of release controlling substances. 
     4.81 g of the powder was added to 5 ml of water. 
     
         ______________________________________  Time  Leakage  (days)        (%)______________________________________  1     0.5  2     0.9  4     1.1  7     1.3  10    1.2______________________________________ 
    
     In this example the leakage of drug was analyzed with a mercurimetric titration method. 
     
         ______________________________________Time        Release in water(days)      (%)______________________________________0.042       600.084       90______________________________________ 
    
     EXAMPLE 2 
     25.8 g of pharmaceutical mixture contains 
     
         ______________________________________Bacampicillin hydrochloride                    0.80 gEudragit ® E 100 microcapsules (64% drug)Fructose                 18.75 gWater                    6.25 g______________________________________ 
    
     Fructose was dissolved in water before the microcapsules were added. 
     The mixture contains 67.5% release controlling substances. 
     
         ______________________________________Time        Leakage(hours)     (%)______________________________________2           0.2______________________________________Time        Release in water(hours)     (%)______________________________________0.008       500.05        90______________________________________ 
    
     EXAMPLE 3 
     31.3 g of pharmaceutical mixture contains: 
     
         ______________________________________Theophylline            0.05 gethyl cellulose microcapsules (72% drug)        Fructose            23.44 g       Water               7.82 g        Sorbitol            20.94 gb       Water               7.82 g______________________________________ 
    
     The two mixtures were prepared according to Example 2. 
     The mixtures contain (a) 75% (b) 72% release controlling substance. 
     
         ______________________________________            LeakageTime             (%)(days)           (a)    (b)______________________________________1                &lt;0.2   0.73                &lt;0.2   --5                &lt;0.2   --7                &lt;0.2   --10               &lt;0.2   --______________________________________Time        Release in water(days)      (%)______________________________________0.21        500.33        90______________________________________ 
    
     EXAMPLE 4 
     31.3 g of pharmaceutical mixture contains: 
     
         ______________________________________Theophylline        0.05 gethyl cellulose microcapsules(72% drug)          Sucrose       9.38 g         Sorbitol      9.38 g          Sucrose       9.38 gb         Glycerol      9.38 g         Glucose        9.38 gc         Fructose      9.38 g         Water         12.5 g______________________________________ 
    
     The three mixtures were prepared according to example 2. 
     The mixtures contain 60% of release controlling substances. 
     
         ______________________________________     LeakageTime      (%)(days)    (a)           (b)    (c)______________________________________1         0.20          &lt;0.2   0.262         0.31          0.35   0.285         0.65          0.82   0.499         1.15          1.77   0.90______________________________________Time        Release in water(days)      (%)______________________________________0.21        500.33        90______________________________________ 
    
     EXAMPLE 5 
     75.1 g of pharmaceutical mixture contains: 
     
         ______________________________________Acetylic salicylic acid               0.100 gcellulose acetate phtalatemicrocapsu1es (69% drug)Sucrose             48.75 gPhosphate buffer (pH 7.0)               26.25 g______________________________________ 
    
     Sucrose was dissolved in the phosphate buffer. The microcapsules were then added. 
     The mixture contains 65% release controlling substance. 
     
         ______________________________________Time     Leakage(days)   (%)______________________________________1        3.5______________________________________Time     Release in phosphate buffer pH 7.0(days)   (%)______________________________________0.008    500.017    90______________________________________ 
    
     EXAMPLE 6 
     
         ______________________________________             a     b        c______________________________________Bacampicillin hydrochloride               0.27 g  0.27 g   0.27 gethyl cellulose microcapsules (70%drug)Sodium bicarbonate  0.40 g  0.40 g   --Mannitol            0.45 g  --       --Sucrose              4.0 g  --       --Water                5.0 g   5.0 g    5.0 g______________________________________ 
    
     The mixtures were prepared according to Example 1. 
     The mixture (a) contains 44% of release controlling substance. 
     The release in water of the microcapsules were the same as in Example 1. 
     
         ______________________________________Time      Leakage (%)(days)    a             b     c______________________________________1         0.5           85    1002         0.94         1.17         1.310        1.2______________________________________ 
    
     EXAMPLE 7 
     Four different microcapsules coated with ethylcellulose were suspended in sorbitol dissolved in water according to following composition. 
     
         ______________________________________Microcapsules          50 mgSorbitol               45.1 gWater                  19.3 g______________________________________ 
    
     The mixtures contain 70% release controlling substance. 
     
         ______________________________________         Leakage in Release in         sorbitol sink                    waterMicrocapsules       (%)     (days) (%)   (h)______________________________________KCl         (86)*   16      21     56    3Paracetaminophene       (91)*   19      21     35    1Flucloxacillin       (89)*   20       1     90    0.5Fenoxymethyl       (83)*   10       1     80    1penicillin potassium______________________________________ *content of active drug in the microcapsule 
    
     EXAMPLE 8 
     0.2 g theophyllin microcapsules according to Example 3 were suspended in different sugar solutions 
     
         ______________________________________Release controllingsubstance               Leakage  Time% (w/w)                 (%)      (days)______________________________________Xylitol       55        13       80Glucose       50        17       40Sorbitol      70        3        80Fructose      75        3        80Fructose-xylitol         19-41     10       80Fructose-xylitol         38-28     6        80Fructose-xylitol         56-14     4        80______________________________________ 
    
     It is thus possible to restrict the leakage in the mixture to only a few percent after almost three months storage in room temperature. 
     EXAMPLE 9 
     65.4 g of pharmaceutical mixture contains: 
     
         ______________________________________Theophyllin wax     1 gcoated microcapsules(52% drug)Sorbitol          45.1 gWater             19.3 g______________________________________ 
    
     The mixture was prepared according to Example 3. 
     The mixture contains 69% release controlling substance. 
     
         ______________________________________Time        Leakage(days)      (%)______________________________________22          0.7______________________________________Time        Release in water(days)      (%)______________________________________0.5         19______________________________________ 
    
     EXAMPLE 10 
     26.31 g of pharmaceutical mixture contains 
     
         ______________________________________Prochloroperazin wax coated                    10 mgmicrocapsules (3.4% drug)Sorbitol                 18 gWater                    8.3______________________________________ 
    
     The mixture was prepared according to Example 3. 
     The mixture contains 70% release controlling substance. 
     
         ______________________________________Time        Leakage(days)      (%)______________________________________12          2.7______________________________________Time        Release in water(days)      (%)______________________________________0.25        28______________________________________ 
    
     EXAMPLE 11 
     27.15 g of pharmaceutical mixture contains: 
     
         ______________________________________Theophylline ethyl     0.15 gcellulose coated microcapsu1es (72%)Polyethyleneglycol (Carbowax ® 400)                  20.25 gWater                  6.75 g______________________________________ 
    
     Polyethyleneglycol was mixed with water and the microcapsules were added. 
     The mixture contains 75% release controlling substance. 
     
         ______________________________________  Time  Leakage  (days)        (%)______________________________________  15    2.4______________________________________ 
    
     The release in water, see Example 3. 
     EXAMPLE 12 
     13.877 g of pharmaceutical mixture contains: 
     
         ______________________________________Erythromycin            0.877 mgcellulose acetatephtalate coatedmicrocapsules (57% drug)Fructose                9.75Water                   3.25______________________________________ 
    
     The microcapsules were added to a solution of fructose in water. 
     The mixture contains 71% release controlling substance. 
     
         ______________________________________Time        Leakage(days)      (%)______________________________________10          &lt;1______________________________________Time        Release in water(days)      (%)______________________________________0.25        46______________________________________ 
    
     RELEASE STUDIES 
     Microcapsules were suspended in 75% release controlling substance solution and after two or three days storage the microcapsules were filtered off and the release of the drug was measured. The microcapsules were placed in a beaker containing either simulated gastric fluid or simulated intestinal fluid at 37° C. in order to simulate the in vivo situation. The stirring rate was 30 rpm. Samples were withdrawn after certain time points and those were analyzed for drug content spectrophotometrically. 
     The results show time to obtain 50, 70 and 90 percent release of the total amount of microencapsulated drug. 
     
         ______________________________________Theophylline microcapsules  Simulated gastric fluid                   Simulated intestinal fluidRelease  (hours)          (hours)(%)    Original  Stored 3 days                       Original                               Stored 2 days______________________________________50     4.2       4.4        3.7     4.470     5.7       5.8        5.5     6.690     6.2       6.4        7.5     8.3______________________________________Acetylic salicylic acid  Simulated gastric fluid                   Simulated intestinal fluidRelease  (%)              (hours)(%)    Original  Stored 2 days                       Original                               Stored 2 days______________________________________50                          0.14    0.2170                          0.22    0.3190                          0.3     0.51 h    12%        8%2 h    25%       15%______________________________________Bacampicillin hydrochlorideEudragit ® E 100 microcapsules  Simulated gastric fluid                   Simulated intestinal fluidRelease  (min)            (min)(%)    Original  Stored 2 days                       Original                               Stored 2 days______________________________________50     0.4       0.8        1.5     370     0.5       0.9        1.8     3.790     0.7       1.0        2.5     5______________________________________Microcapsule compositions as in Examples 7, 9 and 11.          Release in water         Initially                  Storage timeMicrocapsules           (%)   (h)  (days)                                    (%)  (h)______________________________________KCl                     56    3    14    53   3Paracetaminophene       35    1    14    48   1Fenoxymethyl      (a)   80    1     3    81   1penicillin potassiumTheophyllin wax coated (b)           19      12     25    17   12Theophyllin ethyl           46      6       6    50   6cellulose coated (c)______________________________________ (a) according to Example 7 (b) according to Example 9 (c) according to Example 11 
    
     Release studies have also been carried out on the compositions in Example 8. The release rate was performed according to USP XX (method II paddle) 100 rpm in 900 ml 37° water. 
     The release rate is expressed as percent released per hour. The initial release rate was 12%/h. 
     
         ______________________________________Release controlling             Release rate                        Timesubstance         (%/h)      (days)______________________________________Xylitol           9.9        80Glucose           9.7        40Sorbitol          11.7       80Fructose          11.8       80Fructose-xylitol (19-41)             10.5       80Fructose-xylitol (38-28)             11.9       80Fructose-xylitol (56-14)             11.9       80______________________________________ 
    
     The influence on storage time of the microcapsules in the different sink solution is negligible. 
     STABILITY STUDIES 
     Microcapsule suspensions were prepared with sink solutions according to the invention. The suspensions were stored and the drug content was measured with HPLC analysis as an selective and precise method. 
     
         ______________________________________MixturesMixtures notaccording to   (a)   According to Example 6 bthe inven-     (b)   According to Example 6 ction          (c)   According to Example 6 a          (d)   Bacampicillin HCl microcaps.                                 0.36                (72% drug)                ethylcellulose coated                Sucrose          8.32                Water            4.48          (e)   Bacampicillin HCl microcaps.                                 0.36                (72% drug)                ethyl cellulose coated                Fructose         9.6                Water            3.2 cont.          (f)   Acetyl salicylic acid                                 0.72                microcaps. (69% drug)                cellulose acetate phtalate                coated                Sucrose          8.32                Citrate buffer pH 3                                 4.48          (g)   Erythromycin microcaps.                                 0.44 g                (87% drug)                cellulose acetate phtalate                coated                Sucrose          8.32 g                Phosphate buffer pH 7.0                                 4.48 g______________________________________    Storage condition    time         temp    Intact drug*Mixture  (days)       (°C.)                         (%)______________________________________a        1            25       2b        1            25      60c        10           25      91d        7            25      83e        7            25      89f        30           50      70g        30           50      82______________________________________ *initially the amount of intact drug was 100 
    
     The results imply that mixtures according to the invention has an improving effect on the stability of drugs.