Formulation and Evaluation of Controlled Release Floating Tablets of Lamivudine Employing Hpmc K4m and Sodium Alginate

Lamivudine, a BCS Class I synthetic nucleoside analogue, has a a short biological half-life of 5–7 and is mainly absorbed in the upper gastrointestinal tract. The purpose of the study is to develop a controlled release floating tablets of lamivudine employing HPMC K4M and sodium alginate. The floating tablets of lamivudine were prepared employing HPMC K4M and sodium alginate as matrix formers and sodium bicarbonate as an effervescent agent. The tablets formulated were evaluated for tablet weight variation, drug content uniformity, hardness, friability, floating behaviour and in-vitro drug release. All the formulations fulfilled the official requirements for tablet weight variation, drug content uniformity, hardness and friability. Tablets formulated by using a combination of HPMC K4M/sodium alginate and HPMC K4M alone gave a lesser floating lag time when compared with tablet formulated with sodium alginate alone. All the tablets were found to remain buoyant in 0.1N HCl for a period >24h. The drug release from the prepared tablets was found to be diffusion controlled and followed first order kinetics. Non-Fickian diffusion was the drug release mechanism from all tablets formulated. Lamivudine release form the formulations containing 44.5% (F6) and 40% (F7) of HPMC K4M respectively were found to be slow and spread over 24h. Hence HPMC K4M was found to be more suitable as a matrix former than sodium alginate alone in formulation of controlled release floating tablets of lamivudine. INTRODUCTION: The real challenge in the development of an oral controlled-release drug delivery system is not just to sustain the drug release but also to prolong the presence of the dosage form within the gastrointestinal tract (GIT) until all the drug is completely released at the desired period of time . Floating drug delivery systems are gaining importance in the recent days as they can overcome the limitations of the conventional controlled release dosage forms by sustaining the dosage form in the gastric region for the desired period of time and also releasing the drug in a controlled fashion. Lamivudine, a BCS Class I synthetic nucleoside analogue, is commonly employed as a part of highly active antiretroviral therapy (HAART). Prescribed in a dose of 100–150 mg twice a day, the drug is well absorbed in the upper gastrointestinal tract with a short biological half-life of 5–7 h . Decreasing the frequency of medication to a once-aday regimen tends to decrease systemic side effects and improve patient convenience and compliance to HAART in HIV infected patients .