To control drug release is a topic of much interest. Matrix systems were often used as one method to control drug release. Higuchi mathematically showed the drug release properties of matrix systems, 1) and numerous investigations have been carried out since then. Based on the component, matrix systems can be roughly classified into two types, i.e., polymer and wax matrix systems. Drug release from a polymer matrix is likely to be accompanied by dissolution and/or swelling of matrix layer, and the shape and size of the matrix system varies with release time. Thus polymer matrix systems involve complicated conditions. Compared with polymer matrix systems, wax matrix systems are considered to retain the initial form. To control drug release, it is important to maintain some basic properties of the matrix system. Considering the above difference, the release properties of wax matrix systems should be investigated at first.When a wax matrix system is prepared from melted granules of soluble component and wax, troublesome factors such as surface coverage and thickness of wax on the soluble component must be considered. On the other hand, when a wax matrix system is prepared using a physical mixture of soluble component and wax, basic release properties can be estimated by connecting their basic properties and simple factors.Therefore, wax matrix tablets were prepared from a physical mixture, and basic release properties were examined by the measurement of release from the single flat surface or curved side surface of the tablets. ExperimentalMaterials Isoniazid JP (INZ, Yukigousei Yakuhin Kogyo Co.) was pulverized to about 7 mm prior to use. Hydrogenated caster oil (HCO, Kawaken Fine Chemical Co.) was used as the matrix substance. 2) Preparation of Physical Mixture for Wax MatrixThe mixed weight ratio of INZ to HCO powder was fixed at 7 : 3. The appropriate amounts of INZ and HCO powder were physically mixed using an automatic mixer (type S 10, Taiyo Kagaku Kogyo Co.). Preparation of Tablets for Release from One Flat SurfaceThe amount of physical mixture was fixed at 0.50 or 1.20 g for tablets 10 or 16 mm in diameter, respectively. The physical mixture was put into a die and compressed at 1273 kg/cm 2 with flat-faced punch (model clean press correct 12 HUK, Kikusui Co., Ltd.). A tablet was placed at the center of a die of 16 or 20 mm and the appropriate amount of HCO powder was added. Then the content was compressed at 637 kg/cm 2 . Preparation of Tablets for Release from Curved Side SurfaceUsing the appropriate amount of HCO and the physical mixture of 0.50 or 1.20 g, three-layered tablets 10 or 16 mm in diameter were prepared with compression force of 1273 kg/cm 2 . Release Test A dissolution apparatus (model NTR-VS, Toyama Sangyo Co., Ltd.) coupled to a flow cell set in a double-beam spectrophotometer (model 200-20, Hitachi Ind. Co.) via a microtube pump (model MP-3, Tokyo Rikakikai Co., Ltd.) and pen recorder (model 3056, Yokogawa Electric Works, Ltd.) was used. Release measurement was carried out in 900 ml of di...
To control drug release is a topic of much interest. Wax matrix system was often used as one of methods to control drug release, and its release properties were mathematically expressed by Higuchi. [2][3][4] To control a drug release, it is important to obtain some basic properties of matrix system.When the matrix layer was prepared from melted granules of soluble component and wax, some factors such as surface coverage and thickness of melted wax on the surface of soluble component should be considered at least. On the other hand, when the wax matrix layer was prepared from a physical mixture of soluble component and wax, basic properties of matrix system can be estimated by connecting simple factors.It was considered that reservoir type wax matrix tablet having a fixed surface area may provide more basic release property. In the previous paper, 1) a reservoir device wax matrix tablet was prepared from a physical mixture of hydrogenated castor oil and drug (isoniazid) that was the same one in the reservoir. Hence basic release property from and through the wax matrix layer was investigated (abbreviated as INZ : HCO/INZ system). Then tortuosity as a basic property was suggested to be expressed by a function of the porosity.Here, basic release properties of drug (isoniazid) in the reservoir through the wax matrix layer prepared from the physical mixture of hydrogenated castor oil powder and soluble substance, i.e., lactose were investigated (abbreviated as LAC : HCO/INZ system). As a result, comparable release properties were obtained from both LAC : HCO/INZ and INZ : HCO/INZ systems. Hence it was suggested that the time begin to release the drug in reservoir through wax matrix layer and its release rate constant can be roughly prospected from the amount of matrix layer and mixed weight fraction of component in the matrix layer. ExperimentalMaterials Isoniazid JP (INZ, Yukigousei Yakuhin Kogyo Co.) was pulverized prior to use. Lactose (LAC, Meggle D80) was used as the water-soluble ingredient in the matrix layer. Hydrogenated castor oil (HCO, Kawaken Fine Chemical Co.) was used as the matrix substance.1,5) The mean diameters (mm) of INZ, LAC and HCO are 10.6, 9.4 and 10.3, respectively.Preparation of Reservoir Device Tablet Reservoir device tablets having a flat wax matrix layer were prepared. Lactose and hydrogenated castor oil powder were weighed at a given mixed weight ratio for the matrix layer, and were physically mixed together using an automatic mixer (model S 10, Taiyo Kagaku Kogyo Co.) for 10 min.The physical mixture was put into a die having a diameter of 10 mm. After flattening the surface by using the punch, a 50 mg amount of INZ was accumulated on the physical mixture. Then the contents were compressed at 124.8 MPa to make a two-layer tablet. The two-layer tablet was placed at the center of the bottom of a die having a diameter of 16 mm and 600 mg of HCO was added. Then, the contents were compressed at 62.5 MPa. The shape of prepared reservoir device tablet was the same one shown in the previous pape...
The control of drug release is a topic of much interest. Matrix systems are often used as a method to control drug release. Higuchi mathematically showed the drug release properties of matrix systems, 2) and numerous investigations have been carried out since then. According to the Higuchi equation, releases occur infinitely without regard to the amount of soluble component. A point or region where the release process begins to deviate from the Higuchi equation should appear when the amount of soluble component is finite, as is usual with the preparation of a matrix system. A matrix system as a controlled drug-release system may be more useful if its entire release process can be analyzed.Some troublesome situations such as coverage and thickness of wax should be taken into account when a wax matrix system is prepared using the melt method. Therefore a wax matrix system prepared from a physical mixture of a soluble component and wax powder was chosen to obtain the basic release properties. [3][4][5] Applying the Higuchi equation to release in various manners from the wax matrix tablet, release properties and the applicability of the equation or how release processes deviate from the equation were examined. ExperimentalMaterials The samples reported in the previous papers were used. [3][4][5][6] They were isoniazid JP (INZ, Yukigousei Yakuhin Kogyo Co., Japan) and hydrogenated caster oil (HCO, Kawaken Fine Chemical Co., Japan) as a wax powder. The mean diameter of INZ and HCO was 10.6 and 10.3 mm, respectively. Preparation of Physical Mixture for Wax MatrixThe mixed weight ratio of INZ to HCO powder was fixed at 7 : 3. The appropriate amounts of INZ and HCO powder were physically mixed using an automatic mixer (type S 10, Taiyo Kagaku Kogyo Co., Japan) for 10 min. 3-5)Preparation of Wax Matrix Tablets The amounts of physical mixture used were 0.30, 0.50, and 1.00 g for tablets 10 mm in diameter. The physical mixture was put into a die and compressed at 124.8 MPa with a flat-faced punch (model Clean Press Correct 12 HUK, Kikusui Co., Ltd., Japan). These were used for measurement of release from the whole surface of tablet and are abbreviated as T 3 , T 5 , and T 10 based on the amount of the wax matrix tablet. Preparation of Wax Matrix Tablets for Release from Single FlatFaced SurfaceThe wax matrix tablet of 0.50 g (T 5 ) was placed at the center of a die of 16 mm and an appropriate amount of HCO powder was added. Then the content was compressed at 62.5 MPa for measurement of release from the single flat-faced surface of tablets. These tablet are abbreviated as F 10 based on the release surface and tablet diameter. 3)Preparation of Wax Matrix Tablets for Release from Curved Side Surface Using the physical mixture of 0.50 g and an appropriate amount of HCO powder, three-layered tablets 10 mm in diameter were prepared with compression force of 124.8 MPa for measurement of release from the curved side surface of wax matrix tablets. The tablets are abbreviated as C 10 based on the release surface and tablet diameter....
To control release of a drug is a topic of much interest. The wax matrix system was one method often used to control drug release, and its release properties were mathematically shown by Higuchi.2-4) Some basic properties of release from and through the wax matrix layer prepared from a physical mixture of water-soluble component and hydrogenated castor oil were obtained in previous papers. 1,5) When the wax matrix system was prepared from melted granules of water-soluble component and wax, certain factors such as surface coverage and thickness of the melted wax on the surface of the soluble component should be considered. When the wax matrix system is prepared from a physical mixture of soluble component and wax, basic properties of the matrix system can be estimated by simple factors. It was also believed that a reservoir type wax matrix tablet having a fixed surface area may provide more basic release property, and some of the basic release properties obtained were shown in previous papers. 1,5,6) Here, generalization of the release process through the wax matrix layer was examined using a reservoir device tablet having a matrix layer prepared from a physical mixture of lactose and hydrogenated castor oil. The lag time was analyzed by the Higuchi equation and the actual release process after the lag time was analyzed using the zero-order release kinetic equation. ExperimentalThe following descriptions are closely similar to those in previous papers. 1,5) Materials Isoniazid JP (INZ, Yukigousei Yakuhin Kogyo Co.) was pulverized prior to use. Lactose (LAC, Meggle D80) was used as the water-soluble ingredient in the matrix layer. Hydrogenated castor oil (HCO, Kawaken Fine Chemical Co.) was used as the matrix substance. The mean diameters (mm) of INZ, LAC and HCO are 10.6, 9.4 and 10.3, respectively. The true density (g/cm 3 ) of LAC and HCO are 1.53 and 1.03, respectively. Preparation of Reservoir Device Tablet Reservoir device tablets having a flat wax matrix layer were prepared. Lactose and hydrogenated castor oil powder were weighed at a given mixed weight ratio for the matrix layer, and were physically mixed together by an automatic mixer (model S 10, Taiyo Kagaku Kogyo Co.) for 10 min.The physical mixture was put into a die 10 mm in diameter. After flattening the surface with a punch, a 50 mg amount of INZ was accumulated on the physical mixture. Then the contents were compressed at 124.8 MPa to make a two-layer tablet, this tablet was placed at the center of the bottom of a die 16 mm in diameter and 600 mg of HCO was added. Then, the contents were compressed at 62.5 MPa.This system was called the LAC : HCO/INZ system. Release Test Release measurements were carried out in 900 ml distilled water at a paddle rotation speed of 100 rpm at 37°C. The reservoir device tablet was placed in the dissolution apparatus (model NTR-VS, Toyama Sangyo Co., Ltd.) coupled to a flow cell set in a double-beam spectrophotometer (model 200-20, Hitachi Ind. Co.) via a micro tube pump (model MP-3, Tokyo Rikakikai Co., Ltd.), and pe...
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