Instant oral-release capsule containing nifedipine

Abstract: The invention concerns an instant oral-release capsule containing an aqueous or aqueous alcoholic solution of nifedipine, containing a polyalkylene glycol and a polyoxyethylene ester component, the amount of the ester component in the solution being sufficient to prevent precipitation of nifedipine in the mouth of a patient after release of the solution from the capsule. Preferably, the ester component is an ethoxylated hydrogenated castor oil Cremophor RH40. The solution may further contain a second glycol component, especially glycerol.

Description: The invention concerns an instant oral-release capsule containing nifedipine in solution. Pharmaceutical nifedipine preparations in the form of soft gelatin oral-release capsules are of major importance in the treatment of coronary deseases. When needed, a capsule is bitten by the patient, so that the solution is released from the capsule into the patient's mouth. Immediate action of the nifedipine is desired, so that the absorption of the capsule's nifedipine content by body tissues must be as fast as possible; on the other hand, the nifedipine must remain in the patient's body for the required duration. The absorption of solid nifedipine by body tissue proceeds very slowly, so that solid nifedipine preparations are unsuitable for coronary therapeutical applications. The absorption of nifedipine from solutions is much faster. Nifedipine dissolves in aqueous media only to a very small extent, so that aqueous solutions cannot provide the nifedipine concentrations required for therapeutical purposes. Nifedipine dissolves much better in polyalkylene glycols, especially upon moderate warming. In prior art, therefore polyalkylene glycol solutions of nifedipine have been used in an attempt to achieve the required bioavailability of nifedipine. Such prior art capsules are known from DE 22 09 526. This patent discloses an oral-release capsule with a soft gelatin capsule body containing a solution of nifedipine in, substantially, a mixture of polyethylene glycol and glycerol. Such capsules have for years been marketed under the name "Adalat" (TM). Yet these known capsules do not achieve instantaneous maximal bioavailability of nifedipine. One reason for this disadvantage appears to be the fact that nifedipine solubility decreases once the capsule solution is released from the capsule and mixed with aqueous body fluids, especially saliva. Part of the nifedipine is then precipitated from the solution, so that the absorption is slowed down, resulting in a delay in reaching the required nifedipine blood level. For alternative nifedipine formulations, i. e. sublingual sprays, an attempt at overcoming related problems was described in EP 240 484. According to this prior art, a nifedipine spray solution should contain a combination of polyvinylpyrrolidone, copolyvidone, propylene carbonate and an emulsifier. The compositions disclosed in this prior art are not suitable for capsules. For several reasons, especially in view of the problems involved in administering exact nifedipine dosage amounts through spraying, nifedipine sprays are less advantageous than capsules. EP-A-278 168, which is a non-prepublished prior art document, discloses capsule formulations containing an aqueous polyalkylene glycol nifedipine solution, with a sorbitan ester added to prevent precipitation of nifedipine upon cooling. Prepublished EP-A-117 888 discloses drop formulations of nifedipine solutions similar to those of this invention. The object of this prior art is to provide an advantageous alternative to capsule formulations, which are said to be disadvantageous in various aspects. It is therefore an object of the invention to provide an instant oral-release capsule capable of providing instantaneous maximal bioavailability of nifedipine. It is a further object of the invention to provide such a capsule, achieving at the same time substantially the same duration of nifedipine bioavailability in the patient's body as provided by prior art capsules. These and other technical objects and advantages are achieved by an instant oral-release capsule containing an aqueous or aqueous alcoholic solution of nifedipine, a polyalkylene glycol and a polyoxyethylene ester component comprising ethoxylated hydrogenated castor oil, the amount of the polyoxyethylene ester component in the solution being is between 3 and 33 weight percent, especially about 7 to 15 weight percent to prevent precipitation of nifedipine in the mouth of a patient after release of the solution from the capsule. The invention advantageously prevents nifedipine precipitation in the mouth of the patient, after the solution is released from the capsule and mixed with aqueous media such as saliva, gastro-intestinal fluids etc. This is probably largely due to the presence of the polyoxyethylene ester component in the solution, although it is assumed that synergistic effects are present, the polyalkylene glycol and water in the solution assisting the precipitation-preventing action of the polyoxyethylene ester component. The polyoxyethylene ester has hydrophilic and lipophilic groups, which are probably responsible for the precipitation-preventing effect. The ester component can thus be regarded as an emulsifier. A variety of polyoxyethylene ester components are usable in the context of the invention, but of course they must be non-toxic and pharmaceutically acceptable. Preferably, the ester component should also be neutral in taste. Polyoxyethylene ester components usable in the context of the invention comprise ethoxylated glycerides, especially mono- or triglycerides; ethoxylated fatty acid esters; ethoxylated castor oil derivatives and mixtures of two or more of such substances. It is especially advantageous to use ethoxylated hydrogenated castor oil products as the polyoxyethylene ester component; an especially preferred such product is commercially available under the name Cremophor RH40®. Chosing the most suitable concentration of the polyoxyethylene ester component comprising ethoxylated hydrogenated castor oil, that is between about 3 and 33 weight percent, preferably about 7 to 15 weight percent of the solution is substantially a matter of compromise; higher contents of the ester component allow higher degrees of dilution with aqueous media, before precipitation of nifedipine sets in, but on the other hand such higher ester component contents increase the danger of the solution's taste being adversely affected. At the above-mentioned concentrations, taste is practically unimpaired, while no precipitation of nifedipine is observed under usual conditions, neither in the mouth nor in the gastro-intestinal tract. The polyalkylene glycol component of the solution is preferably a polyethylene glycol (PEG). The PEG should have an average molecular weight smaller than 2000; presently, the PEG is most preferred to have an average molecular weight of about 400. The amount of the PEG or other polyalkylene glycol in the solution is preferably between about 50 and 90 weight percent. Presently most preferred is a PEG concentration in solution of about 70 to 85 weight percent. While it is thus possible to use a solution containing (besides water, taste-improving substance if required and, of course, nifedipine) only PEG 400 and Cremophor RH40, especially in a 9 to 1 weight percent ratio, it is presently more preferred to further add a second glycol component to the solution, especially if this second glycol component is glycerol. The amount of this second glycol component, especially glycerol, in the solution can advantageously lie between about 2 and 15 weight percent, and most preferred at about 5 to 10 weight percent. An instant oral-release capsule forming what is presently regarded as the best embodiment of this invention contains about 500 mg of solution, the solution containing about 10 mg nifedipine, about 403 mg polyethylene glycol with an average molecular weight of about 400, about 35 mg glycerol, about 41 mg ethoxylated hydrogenated castor oil Cremophor RH40® and about 9.5 mg water, about 1.5 mg peppermint oil and artificial sweetener being added as taste-improving substances. The capsule body is formed of soft gelatin and contains light-protective pigments, since nifedipine is highly light-sensitive. The capsule body of this embodiment weighs about 200 mg, so that the overall weight of the oral-release capsule is about 700 mg. The invention will now be described in greater detail, comparing the effects achievable through the invention with those of the prior art capsules, similar to those disclosed in DE 22 09 526. For the comparative tests to be described in detail hereinafter, instant oral-release capsules (A) according to the invention were prepared, which only slightly differ from the above-mentioned presently most preferred embodiment of the invention. These capsules had a capsule body consisting of gelatin with a content of glycerol as a softening agent. The capsule body further contained light-protective pigments, namely titanium(IV)oxide, yellow iron oxide, red iron oxide and brown iron oxide. The capsule body further contained minor amounts of sodium benzoate salts. The overall weight of the capsule body was approximately 200 mg. These capsule bodies were each filled with approximately 500 mg of solution. The solution contained 10 mg nifedipine, dissolved in a mixture of about 35 mg glycerol, about 370 mg PEG 400, about 41 mg Cremophor RH40®, about 44 mg water and, as taste-improving substances about 1.5 mg peppermint oil and sweetener (saccharin sodium). The overall weight of the oral-release capsule was thus approximately 700 mg. When these capsules were administered to patients, no unpleasant taste was reported after the patients had bitten the capsules. As a comparison, oral-release capsules (B) closely corresponding to the prior art capsules were prepared, using the same kind of capsule bodies as for the comparison capsules according to the invention. These capsule bodies were again each filled with approximately 500 mg of solution. The solution contained 10 mg nifedipine, dissolved in a mixture of about 35 mg glycerol, about 409 mg PEG 400, about 44 mg water and about 2 mg peppermint oil and saccharin sodium as taste-improving substances. The overall weight of these oral-release capsules was thus also approximately 700 mg. Both kinds of capsules, those according to the invention and those corresponding to prior art, were used in a clinical cross-over study. For this study, 5 patients were chosen, the personal data of which are given in table I. Patient Height (cm) Weight (kg) Age (a) Sex Appln Sequence Smoker 1 KLH 177 72 39 m B/A + 2 KUJ 177 70 21 m A/B + 3 LOG 176 60 31 m B/A + 4 NAG 175 76 29 m B/A - 5 ROL 178 70 25 m A/B + Mean: 176.6 69.6 29.0 SDev: 1.1 5.9 6.8 CV: .01 .08 .23 The capsules were administered orally; the mouth cavities of all patients were normal. In Table I and the following tables, A represents the capsules according to the invention, while B represents the prior art capsules. Table II contains data for nifedipine concentration in serum (ng/ml) after administration of capsules A. Time Patient 1 2 3 4 5 Mean SDev CV 00:00 0 0 0 0 0 0 0 0.000 00:04 0 0 0 0 0 0 0 0.000 00:08 6 9 7 26 12 12 8 0.671 00:12 19 39 11 53 8 26 19 0.733 00:16 35 118 33 117 19 64 49 0.757 00:20 55 121 61 124 31 78 42 0.532 00:30 90 102 47 130 86 91 30 0.329 00:45 78 85 44 105 116 86 28 0.326 01:00 60 69 40 68 132 74 35 0.467 01:30 49 66 28 53 78 55 19 0.338 02:00 25 41 24 35 37 32 8 0.236 03:00 23 27 13 20 37 24 9 0.377 05:00 12 10 5 7 23 12 7 0.603 08:00 8 2 0 4 10 5 4 0.879 10:00 0 0 0 0 6 1 3 2.236 Table III shows the comparison data of nifedipine concentration in serum (ng/ml) after administration of capsules B. Time Patient 1 2 3 4 5 Mean SDev CV 00:00 0 0 0 0 0 0 0 0.000 00:04 0 0 0 0 0 0 0 0.000 00:08 2 0 5 7 21 7 8 1.155 00:12 6 7 6 14 127 32 53 1.675 00:16 8 16 10 22 160 43 66 1.516 00:20 11 24 15 31 167 50 66 1.330 00:30 26 43 24 45 146 57 51 0.890 00:45 22 32 38 49 121 52 40 0.760 01:00 24 33 65 46 111 56 35 0.623 01:30 33 30 39 29 83 43 23 0.529 02:00 40 64 25 25 53 41 17 0.412 03:00 21 30 18 44 36 30 11 0.364 05:00 11 13 5 11 17 11 4 0.387 08:00 5 7 0 9 9 6 4 0.620 10:00 0 0 0 3 5 2 2 1.421 In Figure 1 the average values of nifedipine serum concentration data for capsules A and B are compared for all patients. Table IV lists the areas under the curves (ng/mlxh) for AUC₀₋₁₀. Patient A B 1 198.7 139.8 2 228.4 190.2 3 109.8 119.1 4 216.5 199.9 5 314.3 346.4 Mean 213.5 199.1 SDev 73.1 89.0 CV 0.342 0.447 Table V lists the areas under the curves (ng/mlxh) for AUC 0-∞ . Patient A B 1 225.3 153.0 2 230.5 207.3 3 112.0 120.8 4 223.5 213.2 5 338.9 366.0 Mean 226.1 212.1 SDev 80.3 94.2 CV 0.355 0.444 Table VI lists the concentration maxima (ng/ml). Patient A B 1 89.8 40.4 2 121.0 63.5 3 60.9 64.7 4 130.0 49.2 5 132.0 167.0 Mean 106.7 77.0 SDev 30.7 51.3 CV 0.288 0.667 Table VII lists the time durations (h) for attaining the maxima of table VI. Patient A B 1 0.50 2.00 2 0.33 2.00 3 0.33 1.00 4 0.50 0.75 5 1.00 0.33 Mean 0.53 1.22 SDev 0.27 0.75 CV 0.513 0.619 Table VIII lists the time durations (h) for attaining a serum concentration of 15 ng/ml (t MEC ). Patient A B 1 0.179 0.378 2 0.147 0.258 3 0.212 0.330 4 0.105 0.206 5 0.241 0.115 Mean 0.177 0.258 SDev 0.053 0.103 CV 0.302 0.401 Table IX lists the elimination constants (h⁻¹). Patient A B 1 0.220 0.278 2 0.506 0.287 3 0.517 0.543 4 0.337 0.240 5 0.258 0.251 Mean 0.367 0.320 SDev 0.138 0.126 CV 0.376 0.394 The average terminal half-time for capsules A (invention) results as 1.89 h, while the average terminal half-time for capsules B (prior art) is 2.17 h. As the data show, the required bioavailability levels are reached significantly faster upon administration of capsules A according to the invention. Since in the practical use of nifedipine preparations, it is of the utmost importance to attain the required degree of bioavailability as fast as possible, the advantages provided by the invention are clear.

Claims: An instant oral-release capsule containing an aqueous or aqueous alcoholic solution of nifedipine, a polyalkylene glycol and a polyoxyethylene ester component comprising ethoxylated hydrogenated castor oil, the amount of the polyoxyethylene ester component in the solution is between about 3 and 33 wt.-%, especially about 7 to 15 wt.-% to prevent precipitation of nifedipine in the mouth of a patient after release of the solution from the capsule. Capsule according to claim 1, the polyoxyethylene ester component being substantially of neutral taste. Capsule according to claim 1 or 2, the polyoxyethylene ester component comprising an ethoxylated glyceride, especially a mono- or triglyceride, an ethoxylated fatty acid ester, or an ethoxylated castor oil derivative, or a mixture of two or more of said substances. Capsule according to claim 3, the polyoxyethylene ester component comprising Cremophor RH40®. Capsule according to any one of claims 1 through 4, the polyalkylene glycol being polyethylene glycol. Capsule according to claim 5, the polyethylene glycol having an average molecular weight smaller than 2000. Capsule according to claim 6, the polyethylene glycol having an average molecular weight of about 400. Capsule according to any one of claims 1 through 7, the amount of the polyalkylene glycol in the solution being between about 50 and 90 wt-%, especially about 70 - 85 wt.-% of the solution. Capsule according to any one of claims 1 through 8, the solution further containing a second glycol component. Capsule according to claim 9, the second glycol component being glycerol. Capsule according to claim 9 or 10, the amount of the second glycol component in the solution being between about 2 and 15 wt-%, especially about 5 to 10 wt.-% of the solution. Capsule according to any one of claims 1 through 11, the capsule body being formed of soft gelatin containing light-protective pigment. Capsule according to any one of claims 1 through 12, the capsule containing about 500 mg of solution, the solution containing about 10 mg nifedipine, about 403 mg polyethylene glycol with an average molecular weight of about 400, about 35 mg glycerol, about 41 mg ethoxylated hydrogenated castor oil Cremophor RH40®, about 9.5 mg water and about 1.5 mg taste-improving substances.

Inventors: BROWN MILLER RONALD, SACKLER MORTIMER DAVID, WIMMER WALTER, BROWN MILLER, RONALD, SACKLER, MORTIMER DAVID, WIMMER, WALTER
Applicants: EURO CELTIQUE SA, EURO-CELTIQUE S.A.
Application year: 1988
Main classification: A61K31
IPC codes: A61K31, A61P9, A61K9