Desensitization of Bladder Sensory Fibers by Intravesical Resiniferatoxin, a Capsaicin Analog: Long–Term Results for the Treatment of Detrusor Hyperreflexia
Objectives: To assess the pungency and the desensitizing effects of intravesical resiniferatoxin, an ultrapotent capsaicin analog, in patients with detrusor hyperreflexia.Methods: Fourteen patients with detrusor hyperreflexia were instilled during 30 min, without any form of local anesthesia, with 100 ml (or the bladder capacity if lower than that volume) of 50 or 100 nM resiniferatoxin solutions in 10% alcohol in saline. Patients were evaluated by voiding chart and urodynamic tests (volume to first contraction, maximal cystometric capacity, maximal detrusor pressure, icewater test) at 14, 30, 60, and 90 days and every 3 months thereafterResults: Resiniferatoxin instillation did not evoke pain or temporary worsening of urinary symptoms. Treatment improved or abolished incontinence in 9 out of 12 incontinent patients. Mean urinary frequency decreased from 14.2±6.4 to 10.3±3.2 at 3 months (p = 0.01). At this time point, mean maximal cystometric capacity increased from 182.3±119.8 to 330.0±201.6 ml (p = 0.01) and the ice water test, positive in 13 cases, became negative in 8 of them. Maximal detrusor pressure was not modified by the treatment. The effect was long–lasting, reaching 12 months in 7 cases.Conclusions: The absence of irritative symptoms during bladder instillation of resiniferatoxin and the rapid onset of desensitization make this vanilloid superior to capsaicin for the treatment of detrusor hyperreflexia.