Hydrophilic matrix systems designed with water-soluble polymers, such as Hypromellose, were first introduced in the early 1970's. Since then, development work has concentrated on controlled release technology, and many types of advanced polymers and techniques have become available.
The hydrophilic matrix system is the simplest sustained release technology for oral dosage forms, consisting essentially of a drug and a water soluble, highly viscous polymer. It does not require any other excipient.
In the recent years, advances in this hydrophilic matrix system have allowed more controllable and reproducible drug release by controlling the chemical and physical properties of the polymer. Hydrocel-CR (Hypromellose) is especially suitable for this application, and provides a genuine consistency in the final products.
Hydrocel-CR, USP Hypromellose (HPMC), is designed for a hydrophilic matrix agent having tighter specifications, which is especially suitable for wet granulation and direct compression application.
The matrix system has several advantages as follows,
Figure 1 illustrates the schematic dissolution profile of the matrix tablet. After administration, hydrophilic matrix tablets made with Hyrocel-CR hydrate to form a gel layer, which regulates the drug release pattern. The most important aspect of this matrix system is the homogeneity of HPMC particle distribution in the tablet. The selection of Hydrocel grades affects the initial wetting, swelling, hydration and gel strength. In the first stage, usually within 30 to 60 minutes after administration, before the completion of the gel layer, the polymer particles on the tablet surface become partially hydrated. Sometimes surface erosion or excess dissolution can be observed in tins period. In the second stage, the gel layer is completed, and a steady dissolution of the active ingredient occurs.
For a highly water-soluble drug: Drug release is regulated by diffusion through the gel layer. In the first 30 minutes an excess amount of drug in the gel layer can release. The dissolution profile is shown in Figure 2. The dissolution profile is shown in Figure 2.
For a poorly water-soluble drug: Drug release is regulated by erosion of the matrix tablet. The dissolution curve is comparatively linier as compared with highly soluble drugs. The dissolution profile is shown in Figure 3.
Substitution type of Hydrocel affects hydration speed of HPMC particles and gel strength, which can influence the dissolution profile.
Viscosity of HPMC affects gel strength or erosion rate of the gel in the second stage, and hydration speed in the first stage. The higher the viscosity, the stronger the gel strength and the slower the hydration speed. By selecting the viscosity grade the dissolution profile can be easily controlled.
The content of HPMC in the matrix tablet significantly affects the initial erosion of the tablet in the first stage. To avoid such a risk the content of HPMC should be 20% or higher.
Large particles require longer hydration time, and in this period particles can swell certain volume. Hydrocel-CR has controlled particle size around 99% passing through 100 mesh, which is an ideal particle size for matrix application.
Film coating was developed as undercoating for sugar coating in the 1950's and film-coated tablets were eventually introduced early in the 1970's. Since then much development work aimed at increasing the production rate of film-coated tablets and reducing the cost has been done in order to improve the efficiency of pharmaceutical manufacturing, as well as the bioavailability of drugs, and film coating is now a well-established and effective technique
HYDROCEL is the brand name of Hydroxypropyl Methylcellulose. It has been subject of a continuous program of development quality improvement. Gastro soluble coatings, cellulose, veg capsules of this type are now in wide spread use throughout the world. Although drug properties are the key factor in medicinal formulations, the physical form or the finish of a preparation is also important. HYDROCEL is easy to use as a film-coating material and gives an excellent finish. It is versatile ,and is suitable for many applications in the design of film-coated tablet as well as veg capsule formulations.
In addition, HYDROCEL is effective as a binder, since it does not interact with drugs, and has superior stability, nonionic, character ,etc. HYDROCEL is widely used as a binder for granulation and is available in various viscosity grades for granulation purposes. HYDROCEL can make a valuable contribution in various areas of pharmaceutical technology.
HYDROCEL film has the hardness, but HYDROCEL film is not as brittle as acrylic polymer. Addition of a plasticizer such as polyethylene glycol (PEG 6,000) is effective when highly flexible film is required. When HYDROCEL film is used for film-coating, sometimes Titanium Oxide or Talc is recommended to be added. Fig. 7 and Fig. 8 show the properties of HYDROCEL film containing Titanium Oxide. For the experiment, film with a thickness of 0.1 mm, which was obtained by dissolving HYDROCEL inmethylene chloride ethanol mixture (50:50), adding Titanium Dioxide to the solution and casting is on a glass plate was used. The measurements were performed under the conditions of 20 ±1.0 °C and 65 ±5% RH according to JIS K-6301.
Addition of inorganic substances such as TiO2 in a large amount to a grade of HYDROCEL with low viscosity (Molecular weight) causes a marked decrease in the tensile strength, often leading to occurrence of cracking and detachment. Therefore, when a inorganic substance is added, use of a grade with a relatively high viscosity (Molecular weight) such as HYDROCEL AW 5 or HYDROCEL AW 15 is recommended.