Design and development of nasal mucoadhesive microspheres containing tramadol HCl for CNS targeting

In the present study, tramadol HCl microspheres were designed in order to accomplish rapid delivery of drug to the brain. For this purpose, lower viscosity grade HPMC (E15) was chosen as mucoadhesive polymer and used at different drug/polymer ratios in the microspheres formulations. The spray-dried microspheres were evaluated with respect to the production yield, incorporation efficiency, particle size, mucoadhesive property, in vitro drug release, histopathological study, and radio imaging study in rabbits. DSC and XRD study showed molecular dispersion and conversion of the drug into amorphous form. Size and surface morphology of microspheres was analyzed by SEM and found to be spherical in shape with smooth surface. It was found that the particle size, swelling ability, and incorporation efficiency of microspheres increase with increasing drug-to-polymer ratio. Microspheres show adequate mucoadhesion and do not have any destructive effect on nasal mucosa. In vitro drug release of optimized formulation was found to be 94% after 90 min. The radio imaging study indicated localization of drug in the brain. Hence, tramadol HCl microspheres based on a HPMC E15 may be a promising nasal delivery system for CNS targeting.