Topical effect of intravesical oxybutynin.

Intravesical oxybutynin was instilled into rat bladders in graded doses by repeated catheterization to study the local bladder effects of drug concentration and incidental urinary infection. On the thirteenth day, after 5 doses, bladders were recovered for measurement and histological study. In the highest dose group, systemic absorption from the bladder caused weight loss and cachexia. However, in no group was there any clear evidence of drug-related mucosal or bladder wall change. Instead, the two high dose groups seemed somehow protected from the combined adverse effects of catheterization and infection.