Prospective, randomized, double-blind study of safety and tolerability of intravesical resiniferatoxin (RTX) in interstitial cystitis (IC)

Objective: To determine the safety and tolerability of intravesical resiniferatoxin (RTX) in interstitial cystitis (IC) patients. Materials and Methods: IC patients were instilled with 50 cc of test solution containing either placebo, 0.05 M or 0.10 M RTX in the bladder. Plasma concentration of RTX and its degradant resiniferonol 9-, 13-, 14-orthophenylacetate was measured. Immediate post-treatment blood sampling and cystoscopy were performed. Symptoms were evaluated before treatment, at 4- and at 12-week follow-ups, using VAS indicator for pain, voiding diary, and OLearys IC symptom/problem indices. Results: Among 22 patients observed (ten in 0.10 M RTX, eight in 0.05 M RTX, and four in placebo groups), the most commonly reported adverse event was pain during instillation (80.0%, 87.5%, and 25.0%). No serious adverse events were reported. Conclusions: Use of intravesical RTX in IC patients is associated with important tolerability issues but safe at 0.10 M and 0.05 M.