New Technology of Thermoplastic Coating for Osmotic Pump Tablets: Study on in vitro Drug Release

Abstract

In the preceding reports, a new technology of thermoplastic coating was developed and the properties of the coating membrane (H membrane) were evaluated.1,2 This technology consists of following three steps: hot-melt extrusion for membrane, heat skin coating, and laser melt cutting (abbreviated as HHL;►Fig. 1). Metformin hydrochloride thermoplastic coated tablets (HHL-METF) and nifedipine thermoplastic coated tablets (HHL-NIF) were prepared by this technology. The traditional metformin hydrochloride osmotic pump tablets (METF-OPTs) such as Fortamet, and nifedipine osmotic pump tablets (NIF-OPTs) prepared by spraying cellulose acetate (CA) dissolved in acetone on the surface of tablets are available in the market.3 Water-soluble METF, an inexpensive oral hypoglycemic agent, widely used in type II diabetes, has expanded usage due to its other beneficial effects. METF is mainly absorbed in the upper part of the small intestine after oral administration. It is taken two to four times a day with a half-life of 0.9 to 2.6 hours. In addition, it has a stimulating effect on the gastrointestinal tract. Therefore,METF-OPTswith fewer side effects are developed and marketed abroad.4–6 Water-insoluble NIF, a commonly used antihypertensive drug, should be taken thrice a day with a short half-life. Its large peak/trough ratio of blood concentration can cause significant blood pressure fluctuations, resulting in serious adverse effects. In clinical practice, NIF-OPTs have beenwidely used once daily to better control blood pressure.7 In this paper, in vitro drug release profiles of HHL-METF and HHL-NIF were studied and compared with those of OPTs prepared by the conventional spray coating. The effects of membrane thickness, polyethylene glycol-1,500 (PEG1500)