Purpose: Capsaicin and resiniferatoxin (Sigma Chemical Co., St. Louis, Missouri) administered intravesically are attractive options for treating detrusor hyperreflexia. Because the 2 agents differ in chemical structure and relative potency, possible differences in their clinical and urodynamic effects were investigated in this prospective comparative study.
Materials and methods: A group of 24 spinal cord injured patients with refractory detrusor hyperreflexia were randomly assigned to receive a single dose of 2 mM. capsaicin in 30 ml. ethanol plus 70 ml. 0.9% sodium chloride or 100 nM. resiniferatoxin in 100 ml. 0.9% sodium chloride. Dwell time was 40 minutes with urodynamic monitoring. Urodynamics were performed at baseline before treatment, and after followups of 30 and 60 days. The frequency of daily catheterizations, incontinence episodes and side effects was recorded.
Results: There was no significant urodynamic or clinical improvement in the capsaicin arm at 30 and 60 days of followup. In the resiniferatoxin arm the mean uninhibited detrusor contraction threshold plus or minus standard deviation increased from 176 +/- 54 to 250 +/- 107 ml. at 30 days (p <0.05) and to 275 +/- 98 ml. at 60 days (p <0.01). Mean maximum bladder capacity increased from 196 +/- 75 to 365 +/- 113 ml. at 30 days (p <0.001) and to 357 +/- 101 ml. at 60 days (p <0.001). Daily catheterizations and incontinent episodes were significantly decreased at 30 and 60 days of followup. Autonomic dysreflexia, limb spasms, suprapubic discomfort and hematuria developed in most patients who received capsaicin but in none who received resiniferatoxin.
Conclusions: Intravesical administration of resiniferatoxin is superior to that of capsaicin in terms of urodynamic results and clinical benefits in spinal cord injured patients and it does not cause the inflammatory side effects associated with capsaicin.