Formulation Optimisation and In Vivo Antidiabetic Evaluation of Mucoadhesive Buccal Tablets Incorporating Methanolic Extract of Gymnema sylvestre

Type 2 diabetes mellitus is a rapidly increasing metabolic disorder across Nigeria, with conventional oral antidiabetic drugs frequently requiring multiple daily dosing and associated with gastrointestinal side effects. Mucoadhesive buccal drug delivery offers an alternative route that bypasses hepatic first-pass metabolism and permits controlled sustained release. Gymnema sylvestre, whose leaves contain gymnemic acids with documented antidiabetic activity, represents a candidate botanical active for buccal delivery. This study optimised and characterised mucoadhesive buccal tablets containing methanolic extract of G. sylvestre and evaluated antidiabetic activity in a streptozotocin-induced diabetic rat model. A central composite design was employed for formulation optimisation, with carbopol 934 and hydroxypropyl methylcellulose K4M concentrations as independent variables. Tablets were characterised for bioadhesive strength, drug content uniformity, surface pH, and in vitro drug release. The optimised formulation was administered buccally to diabetic Wistar rats over 28 days, and fasting blood glucose, serum insulin, and pancreatic histopathology were evaluated. Optimised tablets demonstrated bioadhesive strength of 18.4 g and sustained gymnemic acid release over eight hours with surface pH of 6.7. Blood glucose reduction in treated diabetic rats reached 43.6% by day 28, significantly exceeding the oral extract suspension control. Pancreatic histopathology showed partial preservation of islet architecture. These findings support the feasibility of mucoadhesive buccal delivery of G. sylvestre extract as an improved antidiabetic formulation. Keywords: mucoadhesive buccal tablets, Gymnema sylvestre, antidiabetic, formulation optimisation, streptozotocin.