Efficacy and safety of intravesical dimethyl sulfoxide treatment for patients with refractory Hunner‐type interstitial cystitis: Real‐world data postofficial approval in Japan

Objectives To examine real‐world data regarding intravesical dimethyl sulfoxide (DMSO) therapy after official approval as a treatment for Hunner‐type interstitial cystitis (HIC) in Japan. Methods This single institution, retrospective observational study was conducted between 2021 and 2022 to evaluate the outcomes of 30 patients with refractory HIC who received intravesical DMSO therapy according to the approved standardized regimen: administration of DMSO every 2 weeks for a total of 12 weeks. Treatment outcomes were evaluated using a 7‐graded global response assessment scale, O'Leary and Sant's symptom and problem indices (OSSI/OSPI), the overactive bladder symptom score (OABSS), an 11‐point pain intensity numerical rating scale, quality of life (QOL) score, and frequency volume chart variables. Related complications were also documented. Results The response rates at 2, 4, 6, 8, 10, and 12 weeks were 36.7%, 43.3%, 53.3%, 60.0%, 70.0%, and 70.0%, respectively. Compared with baseline, OSSI/OSPI, pain intensity, urinary frequency, and the QOL score improved significantly from 4 weeks of treatment. The OABSS score and functional bladder capacity also showed a tendency toward moderate improvement, but the difference was not significant. The mean duration of symptom relapse after termination of treatment was 6.4 ± 3.9 months. No patients discontinued treatment due to adverse events, although acute bladder irritation during infusion was noted in 21 patients (70%), which disappeared within 3 days. Conclusions This study verifies the safety, moderately durable efficacy, and tolerability of the standard intravesical treatment with DMSO for HIC in Japan.