Raft Forming Drug Delivery Systems: A Comprehensive Review of Formulation Design, Mechanism, Evaluation, and Recent Advances

Abstract

Gastric retention remains a persistent problem in oral drug delivery. Drugs absorbed mainly in the stomach or upper small intestine, or those intended to act locally on the gastric mucosa, often underperform simply because conventional dosage forms clear the stomach too quickly. Raft forming systems were developed to address this, and they do so in an unusual way: rather than relying on a rigid floating device, they generate a soft, low density gel  a “raft”  directly inside the stomach. The raft forms when a polymer, typically sodium alginate, contacts gastric acid and gels, while gas released from a bicarbonate or carbonate source becomes trapped within that gel and keeps it afloat. First used in antacid products for gastroesophageal reflux disease, the same underlying chemistry has since been adapted for sustained drug release, antibiotic delivery against Helicobacter pylori, and several other applications requiring prolonged gastric residence. This review traces that development how rafts form and why they float, what goes into formulating one, how they are tested, where they have found clinical use and considers newer approaches, including nanoparticle loaded rafts, mucoadhesive variants, and 3D printed dosage forms, that are being explored to extend the technology further.