Evaluation of in Vitro and in Vivo Transdermal Absorption of Solifenacin Succinate.

Solifenacin (Sol), an antimuscarinic agent has been widely used for the treatment of overactive bladder. Transdermal formulations can be administered without water as well as absorbed slowly into the blood over a long period of time. The aim of this study was to develop cream and tape formulations of Sol, and evaluate the transdermal permeation and absorption of the drug from the two formulations in vitro and in vivo, respectively. In the preparation of cream formulation, Sol succinate was dissolved in purified water, and the mixture was added to the hydrophilic cream. Then, aqueous sodium hydroxide was added to the cream. In the tape formulation, Sol succinate was dissolved in a solvent with propylene glycol, diisopropanolamine, triethyl citrate, and EUDRAGIT E100. The dissolved solvent was poured onto a polyethylene film. Cream (5%) and tape (15%) formulations demonstrated high skin permeability. Addition of an adsorption enhancer (N-methyl-2-pyrrolidone) did not further increase the level of skin permeability. In subsequent in vivo experiments in rats, both the cream and tape formulations led to slow absorption of Sol into plasma, with increased t _1/2 compared with oral administration. Plasma Sol concentrations peaked 24 h after transdermal application and the drug was still detectable in plasma 72 h after application. Additionally, the cream (5%) and tape (15%) formulations resulted in a higher area under the plasma concentration vs. time curve from 0 to 72 h (AUC _0-72 ) compared with oral formulation (30 mg/kg). In conclusion, significant in vitro permeability and in vivo absorption of Sol from the transdermal formulations were observed.