Gastro-retentive oral drug delivery systems: a promising approach for narrow absorption window drugs

Abstract

Drugs with narrow absorption window (NAW) are those drugs that are absorbed from a specific region (most notably first part) of the gastrointestinal tract. Therefore, typical modified/sustained release formulations of those drugs cannot provide a true long-acting drug release. Once the dosage form has passed the absorption sites at the specific regions of the small intestine; the drug is no longer absorbed from the modified release dosage form and the bioavailability is adversely decreased. While there are many pharmacological classes such as centrally acting skeletal muscle relaxants, anti-parkinsonism drugs and anti-infective belong to NAW drugs and are required to be formulated in modified release dosage forms. Modified release dosage forms based on gastroretentive technologies could hold a promise. Such dosage forms aim to release drugs in the upper part of the gastrointestinal tract especially in the stomach in a controlled release manner that might provide sustained release characteristics without sacrificing much of total bioavailability. This review provides critical appraisal on different technologies, polymers, candidate drugs for gastroretentive technologies.