Gastroretentive Bilayer Tablets: A Comprehensive Review on In-Vitro, Ex-Vivo, and In-Vivo Evaluation Parameters

Abstract

Gastroretentive drug delivery systems (GRDDS) are used to enhance the bioavailability of drugs like narrow absorption window, drug with pH dependent solubility, and drugs with local gastric action having most efficient absorption in stomach or upper gastrointestinal tract. Bilayered tablets are a good choice where one layer is designed to release immediate dose and the other is for sustained release. This method enhances the absorption of medications and reduces the frequency of doses administered to the patient. On the other hand, just making these tablets is the first step, so they must go through stringent testing to verify their mechanical strength, cure adhesion, buoyancy or swelling, drug release profile, in-vivo studies, etc. This study reviews the prominent evaluation methods of gastroretentive bi-layer tablets. In-Vitro testing is performed to check the inherent properties like hardness, weight uniformity and floating lag time. Moreover, the total floating duration, swelling behaviour and the complete dissolution kinetics are also evaluated. The employed animal gastric mucosa in Ex-Vivo studies assesses swelling and mucoadhesion on actual tissues and residence time. In-vivo methods like X-ray, gamma scintigraphy, and pharmacokinetic studies can clearly indicate gastric retention time and improvement of drug bioavailability and clinical efficacy. The integration of these methods works the best. It does provide reproducible preliminary data. Ex-vivo does give us more relevant and physiological data. In-vivo tests do check if it’s working or not in the proper organism. Bringing these formulations to patients successfully relies on an effective evaluation strategy that complies with regulatory standards.