PURPOSE: We evaluated the influence of tolterodine extended release on human bladder afferents. The afferents were assessed by determining the bladder electrical perception threshold using endovesical electrical stimulation at different potentially neuroselective frequencies.
MATERIALS AND METHODS: A total of 30 healthy female subjects with a mean +/- SD age of 23.6 +/- 2.3 years and a mean body mass index of 20.5 +/- 1.7 kg/m2 were assigned to 3 groups of 10 each in a double-blind manner, including group 1-placebo, group 2-4 mg tolterodine extended release and group 3-8 mg tolterodine extended release. The investigation was performed using an 8Fr catheter for filling and stimulation that was placed at the bladder neck in a 100 ml filled bladder. Bipolar stimulation was performed using 2.5, 5 and 250 Hz stimuli. Subjects were asked to indicate sensation by pressing a button. Electrical perception thresholds were determined using the method of levels. Electrical perception thresholds were determined before and 4 hours after medication.
RESULTS: No significant change in the electrical perception threshold after treatment could be found among the groups at 2.5, 5 and 250 Hz (p = 0.178, 0.817 and 0.365, respectively). There was a tendency in the tolterodine extended release groups toward an increased electrical perception threshold at 250 Hz (4 mg less than 8 mg). In most cases electrical stimulation with 2.5 and 5 Hz was described as a slight twinge, tickle or desire to void. Stimulation with 250 Hz was the most uncomfortable one, described as a strong, distinct twinge or burning "like urinary tract infection."
CONCLUSIONS: Although a tendency was observed toward an increased electrical perception threshold at 250 Hz, this study showed no significant effect of tolterodine extended release on the bladder electrical perception threshold.