Design and evaluation of a chitosan microsphere-hydrogel system for sustained topical delivery of tramadol hydrochloride

Conventional tramadol formulations are limited by frequent dosing, variable plasma levels, leading to side effects and poor patient compliance. To address this, design and develop a unique dual-polymer system that incorporates tramadol-loaded chitosan microspheres into a chitosan-guar gum hydrogel matrix. TMH-loaded chitosan microspheres were prepared using ionic gelation with sodium tripolyphosphate as a crosslinker. The optimized microspheres (TM4) had a smooth spherical shape, significant drug entrapment (99.15%), and controlled release of 84.3% over 12 h by Fickian-diffusion. These TM4 microspheres were incorporated into a chitosan-guar gum-based hydrogel to form a dual-polymeric matrix. The developed microsphere-loaded hydrogel revealed significantly improved clarity, pH 6.9 (skin compatible), spreadability (18.64 g cm/s), viscosity (72,860 cP), and sustained release (78.42%, 8 h), outperforming both plain and a commercial formulation. The SEM, FTIR, and DSC showed stability and no drug–polymer interaction. The formulation demonstrated prolonged in vitro drug release across a synthetic cellulose acetate membrane and showed acceptable physicochemical properties, skin compatibility, and short-term stability. These findings support the potential of the dual-matrix system as a sustained topical delivery platform for tramadol hydrochloride. However, further ex vivo skin permeation and in vivo pharmacokinetic studies are required to confirm its transdermal drug delivery potential.