Intravesical resiniferatoxin for patients with neurogenic detrusor overactivity

Background: Resiniferatoxin (RTX), a substance isolated from some species of Euphobia, is a specific C-fiber neurotoxin which produces desensitization rather than excitation. At first, we performed intravesical RTX therapy on eight patients with neurogenic detrusor overactivity. After we confirmed the safety and efficacy, a Japanese RTX study group was organized and a new protocol made. The multicenter trial was performed in Japan. However, the efficacy of the treatments was different among the institutions. Therefore, we have compared the results between the first protocol and the new one at our hospital. Methods: The first and second protocol involved the RTX solution (30 mL of 500 nM, and 100 mL of 1 μM, respectively) being instillated in the bladder for 30 min by almost the same procedures. Effects on bladder function were evaluated during treatment and at follow up. Results: For the first and second protocols, six out of eight patients noted symptomatic improvement while two patients did not notice any change in the degree of incontinence for one month. The mean urodynamic bladder capacity had significantly increased from 138.0 ± 64.4 mL to 227.3 ± 112.4 mL and 133.1 ± 43.3 mL to 247.0 ± 102.3 mL 1 month after RTX treatment for the first and second protocols, respectively (P < 0.05). No severe side-effects were seen in either group. Conclusion: Intravesical RTX improved bladder capacity in patients with neurogenic detrusor overactivity in both protocols. The concentration of RTX did not exhibit any change in the effect and safety in our hospital. Intravesical RTX is a promising treatment for neurogenic detrusor overactivity.