Design of transparent film-forming hydrogels of tolterodine and their effects on stratum corneum.

A transparent film-forming hydrogel formulation for tolterodine was developed using ternary phase diagram and Box-Behnken design (BBD). Carbopol 980 (neutralized by triethanolamine), hydroxypropyl cellulose (HPC), hydroxypropyl methyl cellulose (HPMC) and Tween 80 were used as matrices. Solvent was the mixture of water and ethyl alcohol. The measured 24 h cumulative drug release rate (86.02%) was consistent with the predicted value (85.42%) in mice. Steady-state flux (J) of tolterodine in optimized formulation across rat full skin, epidermal, dermis and subcutaneous tissue were 15.83, 18.55, 37.15 and 81.82 μg cm(-2) h(-1), respectively. Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) results suggested that the hydrogels could impact lipid status in SC, which was consistent with Ea (8.638 kcal/mol) of tolterodine from optimized formulation in rats. In the pharmacokinetic studies, sustained-release over 24 h and absolute bioavailability of the hydrogels (24.53%) was higher than tolterodine tablets (15.16%) in rats. The hydrogels were suitable for systemic administration of tolterodine for the treatment of overactive bladder.