Intravesical oxybutynin affects bladder permeability

To investigate the effects of intravesical application of oxybutynin chloride on bladder permeability we designed an animal model. Female Guinea pigs were given 3 different test solutions; phosphate buffered saline (PBS), 50% acetone and 1.27 × 10-2 M oxybutynin chloride solution. Then 99mTc-DTPA 45 ?Ci in 2 ml normal saline was instilled into the bladder lumen in each animals and allowed to dwell for 30 minutes. At the end of exposure time, the net count data in each 1 ml serum sample were corrected for radioactive decay and converted to the total percentage of administered dose. 99mTc-DTPA absorption percentages of both acetone and oxybutynin groups were significantly higher than that of PBS group (mean 3.2 ± 2.9% p < 0.001). Intravesical oxybutynin application increases bladder permeability 5 times compared with PBS administration. This observation can also explain how rapid absorption of oxybutynin through the bladder into the systemic circulation occurs.