Six studies were included (n=225 patients). These included three randomised controlled trials (RCTs, n=203 patients), two uncontrolled prospective studies (n=17 patients) and one case series (n=5 patients). One RCT had a sample size of 163; in the other studies, the sample size ranged from 4 to 22. The authors stated that two of the RCTs were of good quality but provided no further details.
Unless otherwise stated resiniferatoxin was given as a single instillation.
The largest RCT (n=163 patients) reported no statistically significant difference between a resiniferatoxin and placebo in overall symptoms, pain, nocturia, urgency, frequency and void volume. One smaller RCT (n=22 patients) reported no statistically significant relationship between resiniferatoxin dose and an overall score or symptom index. The other small RCT (n=18 patients) reported that resiniferatoxin was associated with a statistically significant reduction in nocturia and pain at four weeks (p<0.01) and a significant reduction in frequency at four weeks (p<0.01) and 12 weeks (p<0.05).
The uncontrolled studies reported a decrease in bladder pain in two of four patients (one study, n=4 patients), a 58% overall satisfactory improvement rate with significant improvement in pain and quality of life (one study that evaluated multiple instillations, n=13 patients) and a significant reduction in frequency, nocturia and pain (one study that evaluated prolonged infusion, n=5 patients).
Two uncontrolled studies (n=13 and 18 patients) reported no significant change in videodynamic or urodynamic measures.
Serious adverse events were reported in two patients with severe abdominal pain.