Intravesical oxybutynin in patients with posterior rhizotomies and sacral anterior root stimulators

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Abstract
This report investigates the use of intravesical oxybutynin in spinal injury patients, who have had dorsal rhizotomies to abolish reflex detrusor activity and void with S2, S3, and S4 stimulation, done with the Brindley anterior root stimulator.Six male patients (age range 27 to 56, mean 36 years) who have had Brindley anterior root stimulators implanted were included in this study. Video urodynamic assessment was done and 10 mg of oxybutynin hydrochloride was instilled through the urethral catheter. This was left in the bladder for 60 minutes and video urodynamics were repeated. Voiding, both pre and post oxybutynin, was achieved with sacral root stimulation.Peak detrusor pressure (Pves) during voiding in the 6 patients before oxybutynin instillation was 89, 154, 90, 60, 56, and 80 (mean 88.2) cm of water. Post oxybutynin the pressures were 83, 163, 95, 40, 30, and 68 (mean 79.8) cm of water. The peak flow rate (Qmax) pre oxybutynin was 32, 24, 20, 20, 12, and 28 (mean 22.7) ml per second and this changed to 28, 31, 18, 24, 10, and 32 (mean 23.8) ml per second. This shows no difference in the detrusor pressure (P = 0.2) and flow rate (P = 0.54) pre and post oxybutynin instillation into the bladder.Effectiveness of oxybutynin is attributed to a combination of M3 receptor antagonism in the smooth muscle and direct spasmolytic, local anaesthetic and calcium channel blocking action. Its therapeutic benefit is limited by the ami cholinergic side effects (40–80%) and recent studies have shown the intravesical route to be effective and better tolerated. However in this study it has been ineffective in abolishing any detrusor contractions generated by S2, S3, and S4 stimulation.