Sustained-release multi-granule tablet

Abstract: A sustained-release multi-granule tablet is obtained by compressing sustained-release granules, which contains a basis, and a formulation adjuvant. Each of the granules has been coated in advance with a layer of the formulation adjuvant and/or a layer of a mixture of the formulation adjuvant and the basis. The tablet releases an active substance at a suitable velocity into the digestion tract, resulting in that the inbalance in the absorption of the drug in each patient and among individual patients is minimized to achieve maximum bioavailability.

Description: BACKGROUND OF THE INVENTION 1) Field of the Invention: This invention relates to a sustained-release multi-granule tablet useful in the field of therapy. More specifically, this invention is concerned with a tablet of the multiple unit type, in which sustained-release granules are contained as a unit. 2) Description of the Prior Art: Sustained-release tablets are of such a preparation form that is intended to lighten the sufferance of patients by reducing the frequency of administration and at the same time to improve the usefulness of a drug to the maximum in view of both advantageous effects and side effects of the drug. A certain type of sustained-release tablets take the form of the so-called multiple unit. Namely, a drug is firstly converted into a sustained-release particulate or granular form by a suitable method. A powdery or particulate substance composed of one or more formulation adjuvants is then mixed. The resulting mixture is finally compression-formed or compressed into desired weight, shape and size. In a drug preparation of the multiple unit type, the drug is divided into a number of granules and is released as an active substance at a suitable velocity into the digestion tract so that the imbalance in the absorption of the drug in each patient and among individual patients is minimized to achieve maximum bioavailability. As typical preparation forms, there are known for example spansule-type capsules in each of which micropills are enclosed in a capsule and tablets of the multiple unit type. The present invention relates to the latter preparation form. The following two problems have been pointed out for many years as drawbacks of tablets of the multiple unit type. The problem of variations in quality is mentioned first of all. In the case of compression-forming, it is generally known that inconsistent mixing occurs due to differences in mixing ratio upon mixing operations, segregation caused by differences in granule number or shape among increments, etc. When tablets of the multiple unit type are produced from sustained-release granules, variations arise as to the contents of the sustained-release granules and the associated granules as a formulation aid by their numbers and their mixing ratio. Regarding the above-mentioned problem, there is a study conducted by Dr. Shigeo Miwa ["Introduction to Chemical Engineering II", Chapter: "Mixing" (Asakura Shoten)]. From a theoretical curve between the numbers of granules of a drug administered and variation coefficients when the mixing proportion of granules containing an active component is varied in various ways, it is indicated that the variation becomes smaller as the proportion of granules containing the active component increases and the number of granules administered increases. Let's now contemplate to reduce the variations by applying the above theory to a drug preparation of the multiple unit type. If the proportion of granules containing the active component is increased, the granules are however caused to agglomerate together upon their compression forming and the granules hence become difficult to disperse at the time of the disintegration of the tablet, thereby leading to the loss of the inherent function of the multiple unit. If the number of granules is increased on the other hand, another drawback arises that the preparation form becomes greater. As the second problem, granules undergo deformation or destruction by high-pressure compression at the time of compression-forming so that the sustained-release function of each unit granule is lost. This may be considered as the largest drawback of multiple unit tablets in a certain sense. FR-A-2 150 903 discloses a compressed tablet containing a basis in the form of granules which are coated with a formulation adjuvant. US-A-3,906,086 refers to granules of a basis being covered with a formulation adjuvant and pressed into tablets. SUMMARY OF THE INVENTION The present inventors have conducted an extensive research with a view toward developing a process for the formulation of multiple unit tablets which are free from occurrence of agglomeration of granules upon compression forming, are small and have smaller variations in the content of an active component. As a result, it has been found that small tablets of the multiple unit type having smaller variations in the content of an active component can be obtained by coating the surfaces of sustained-release granules as nuclei with layers of a formulation adjuvant and/or layers of a mixture of the formulation adjuvant and a basis and then compression-forming the thus coated granules. In one aspect of this invention, it is thus provided a sustained-release multi-granule tablet obtained by compression-forming sustained-release granules, which contains a basis, and a formulation adjuvant. Each of the granules has been coated in advance with a layer of the formulation adjuvant and/or a layer of a mixture of the formulation adjuvant and the basis. By coating the outer surfaces of sustained-release granules with a formulation aid or the like and forming protective coating films thereon, the discreteness of each granule can be enhanced so that their agglomeration upon compression-forming or their deformation or destruction can be avoided. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 diagrammatically shows results of disintegration tests of Tablets A, B and C obtained by the coating method in comparison with results of a disintegration test of a tablet obtained by adding powder; Figure 2 is also a diagrammatic representation of the results of the disintegration tests of Tablets A, B and C in comparison with results of a disintegration test of a tablet obtained by adding granules; Figure 3 diagrammatically illustrates results of disintegration tests of Tablets D, E and F in comparison with the results of the disintegration tests of Tablets A, B and C; and Figure 4 diagrammatically depicts results of disintegration tests of Tablets G, H and I. DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS Illustrative examples of the formulation adjuvant in the present invention may include excipients, binders, disintegrators, etc. As exemplary excipients useful in the practice of this invention, may be mentioned Avicel 101, Avicel 301 and Avicel 102 (all trade names, crystalline celluloses), lactose, mannitol, sucrose, corn starch, dextrin, silicic acid, magnesium silicate, aluminum silicate, etc. As exemplary binders, it is possible to use HPC-L (trade name, hydroxypropylcellulose), PVPK30 and PVPK90 (both trade names, polyvinyl pyrrolidone), PEG6000 (trade name, polyethylene glycol), methylcellulose, etc. As illustrative disintegrators, CMC, CMC-Ca, sodium crosscalmerose and the like may be used. The preparation, coating and tablet making operations of sustained-release granules in the present invention can be carried out respectively by conventional procedures such as those mentioned below. i) Preparation of basis granules (nuclear granules) to be used as nuclei : Using a usual cylindrical granulator, basis granules are prepared in accordance with the cyclindrical granulating method. ii) Coating in layers : The coating is conducted by the rolling granulating method. Namely, nuclear granules and an excipient were mixed in a routine mixer such as super mixer or Henschel mixer. Upon coating, one or more formulation adjuvants such as binders, disintegrators and lubricants may also be added as needed. iii) Tabletting : Tabletting is conducted using a usual tablet machine. There are the wet tabletting method and dry tabletting method. Tabletting may be effected by either one of these methods. Examples: The constitution and advantageous effects of this invention will hereinafter be described specifically by the following Examples. It should however be borne in mind that the present invention is by no means limited by the following Examples. Example 1: Sustained-release granules, which had been obtained by granulating in a cylindrical granulating machine equipped with a screen of openings of 0.5 mm across (Model: HV-G; manufactured by Hata Tekkosho K.K.) and then sifting the resultant granules to 16 mesh - 60 mesh, were charged in a 1-ℓ Henschel mixer. While mixing the granules with occasional addition of corn starch and an ethanol solution of PVP K30 in small quantities, the sustained-release granules were coated in layers to give the proportions shown in Table 1. Two hundred milligram portions of the thus-obtained samples were separately weighed precisely and then compression-formed under 400 kg/=8mm by a material testing machine (manufactured by Shimadzu Corp.), whereby tablets were obtained separately. In the same manner as described above except for the omission of the ethanol solution of PVP K30 as a binder, additional tablets were separately obtained by adding corn starch as is, i.e., in the form of powder or in the form of granules at the same ratio of corn starch to sustained-release granules. Disintegration tests were then conducted with respect to the layer-coated tablets (invention products), powder-added tablets and granule-added tablets, all of which had been obtained above. Results are shown diagrammatically in Figures 1 and 2. In each of the drawings, the ratio of corn starch to sustained-release granules is plotted along the axis of abscissas while the disintegration time is plotted in minutes along the axis of ordinates. Plotted points have the following significance: In addition, coagulation tests were conducted with respect to those tablets. Namely, each tablet was added with 10 mℓ of water in a weighing bottle. Twenty-four hours later, the disintegration residue was collected by filtration. The coagulated matter (formed by coagulation of two or more granules) in the disintegration residue was then weighed. Results are shown in Table 2. From these results, it is understood that the tablets obtained respectively by the powder-adding method and the granule-adding method are not different in disintegration time from the tablets formed solely of the sustained release granules up to at least a corn starch/sustained-release granule ratio of 50/100 but a significant reduction in disintegration time is observed at a corn starch/sustained-release granule ratio as small as 20/100 in the case of the invention tablets obtained by the layer-coating method. It is also envisaged that the layer-coating method permits the formulation of tablets without coagulation of sustained-release granules. Example 2: Tablets D, E and F were obtained separately in the same manner as in Example 1 except that portions of corn starch in the respective compositions of Example 1 were replaced by a disintegrator, CMC-Ca, as shown in Table 3. Disintegration and coagulation tests were conducted with respect to those tablets. Results of the disintegration tests will be compared with those of Tablets A, B and C in Example 1. Results of the disintegration and coagulation tests are shown in Figure 3 and Table 4 respectively. In Figure 3, plotted points ○ correspond respectively to Tablets D, E and F while plotted points  correspond respectively to Tablets A, B and C of Example 1, namely, added with no CMC-Ca. Namely, the disintegration time of the sustained-release granules was shortened further by the addition of a disintegrator such as CMC-Ca to the layer-coated granules and moreover, no coagulation of the sustained-release granules was observed after their disintegration. Example 3: Tablets G, H and I were obtained in accordance with the composition of Example 2 except that corn starch and CMC-Ca were changed respectively to lactose and sodium crosscalmerose. Disintegration and coagulation tests were conducted with respect to those tablets. Results are shown in Figure 4 and Table 5 Respectively. Example 4: Sodium crosscalmerose, a disintegrator, was separately coated as layers in varied amounts on the surfaces of sustained-release granules. After compression, the state of coagulation of the granules in each tablet was observed. Namely, sodium crosscalmerose was coated as layers on the surface of the sustained-release granules in the same manner as in Examples 1 - 3. Then, 200-mg portions of the thus-obtained samples were separately weighed precisely and compression-formed under punching pressures of 200 kg and 400 g/=8.0 mm by means of the material testing machine (manufactured by Shimadzu Corp.). Coagulation and disintegration tests were then conducted separately with respect to the thus-obtained tablets. Compositions and test results are shown in Table 6. In Table 6, the sample obtained by compression-forming the sustained-release granules alone (Tablet J) did not disintegrate even 24 hours later. In the case of the samples coated as layers with sodium crosscalmerose on the other hand, no coagulation of the sustained-release granules was observed, for example, at a proportion of the coated layers of 1.0 wt.% and up when the compression pressure was 200 kg/=8.0 mm. In the case of Tablet G with about 20% of lactose added based on the sustained-release granules, the tablet did not disintegrate completely and about two thirds remained undisintegrated even after an elapsed time of 60 minutes later in the disintegration test. However, no coagulation among the sustained-release granules was observed in the coagulation test. It is hence appreciated that when lactose is added in a small amount, the disintegration time becomes longer but no coagulation occurs among the sustained-release granules and the tablet undergoes disintegration similar to that of a multiple unit. Example 5: Using a 20-ℓ Henschel mixer, portions of sustained-release granules were separately layer-coated to give mixing proportions (weight proportions) shown in Table 6. The formulation procedure of Examples 1 -3 was followed. Each portion of the sustained-release granules was charged in the mixer. Thereafter, the excipients, disintegrator and binder were coated as layers on the sustained-release granules while adding their ethanol solution little by little to the sustained-release granules. Results of disintegration and coagulation tests are also shown in Table 7. Example 6: Tablets, which were able to show dispersion similar to that of multiple units, were formulated by using sustained-release granules containing bunazosin hydrochloride as a basis. The sustained-release granules are cylindrical granules prepared by using a screen whose openings had a diameter of 0.5 mm. When the sustained-release granules were compression-formed as they were, they did not integrate and did not show dispersion similar to that of multiple units. Using a fluidized centrifugal granulator CF 360 (trade name; manufactured by Freund Sangyo K.K.), formulation adjuvants suspended in 2400 mℓ of ethanol were added little by little so that they were caused to deposit as layers on the sustained-release granules containing bunazosin hydrochloride and the following composition was achieved. Composition (parts by weight) Sustained-release granules (content of bunazosin hydrochloride: 10%) 750 Lactose 705 CMC-Ca 30 HPC-L 15 The thus-obtained layer-coated granules were added with calcium stearate in an amount of 0.2 wt.%. Under punching conditions consisting of a revolution speed of 30 rpm and a compression pressure of 0.6 - 0.7 ton/punch, the resultant mixture was then formed into tablets at a rate of 75 mg per tablet by punches having a diameter of 5.5 mm. Results of disintegration and coagulation tests are as follows. Test results Disintegration time (6 tablets) 2.6 - 9.3 minutes Proportion of coagulated matter 0 wt.% In addition, a dissolution test was also conducted by the puddle method. Results are given below. The test was carried out under the following conditions. Namely, the tablets were dissolved for 2 hours with the first solution of the Japan Pharmacopoeia and after adjustment of the pH, the dissolution was continued with the second solution of the Japan Pharmacopoeia. Example 7: In order to use coated layers as fast-acting portions of a basis, bunazosin hydrochloride was added as a basis in the coated layers. Tablets were prepared by the same formulation procedure and under the same formulation conditions as those employed in Example 5. Composition and respective test results are as follows: Composition (parts by weight) Sustained-release granules (content of bunazosin hydrochloride: 8%) 750 Bunazosin hydrochloride 15 Lactose 690 CMC-Ca 30 HPC-L 15 Results of disintegration and coagulation tests Disintegration time (6 tablets) 9.4 - 11.8 minutes Proportion of coagulated matter 0 wt.%

Claims: Process for preparing a sustained-release multigranule tablet containing a basis which comprises coating the surfaces of sustained-release granules as nuclei with layers of a formulation adjuvant and/or layers of a mixture of the formulation adjuvant and a basis and then compression forming the thus coated granules. Process for preparing the tablet as claimed in Claim 1, wherein each of the granules is coated with the layer of the formulation adjuvant. Process for preparing the tablet as claimed in Claim 1, wherein each of the granules is coated with the layer of the mixture of the formulation adjuvant and the basis. Process for preparing the tablet as claimed in Claim 1, wherein each of the granules is coated with the layer of the formulation adjuvant and the layer of the mixture of the formulation adjuvant and the basis respectively. Process for preparing the tablet as claimed in Claim 1, wherein the formulation adjuvant is one or more substances selected from crystalline cellulose, lactose, mannitol, sucrose, corn starch, dextrin, silicic acid, magnesium silicate and aluminum silicate.

Inventors: ANDOH HIDENOBU, MIYAKE YASUO, WATANABE SUMIO, ANDOH, HIDENOBU, MIYAKE, YASUO, WATANABE, SUMIO
Applicants: EISAI CO LTD, EISAI CO., LTD.
Application year: 1987
Main classification: A61K9
IPC codes: A61K9, A61K31