To determine the efficacy of pentosan polysulfate (Elmiron) compared to placebo in the treatment of interstitial cystitis.

The data sources used were MEDLINE, Excerpta Medica, and International Pharmaceutical Abstracts databases, and the manufacturer. Bibliographies of articles obtained were reviewed. The keywords used were pentosanpolysulfate, pentosanpolysulfate sodium, and pentosan. Inclusion criteria were blinded selection of English language, prospective, randomized, placebo-controlled comparative trials; >-8 weeks' duration; >-300 mg daily; adult humans with >- 1 symptoms including pain, urgency, frequency, and nocturia; symptoms for >-12 months; normal urinalysis; negative findings for urine culture and cytology. Exclusion criteria were hemorrhagic cystitis; drug-, microbial-, or radiation-induced cystitis; carcinoma in situ; other influencing diseases. The outcome of success was defined as a >-50% decrease in pain, urgency, frequency, and nocturia. The number of successes was extracted by blinded investigators, treating withdrawals as failures. The percentage difference in success rates of pentosan polysulfate and placebo, and the number needed to treat (NNT) were determined for each variable; P values and 95% confidence intervals (Cls) were determined for combined data. Homogeneity of effect was determined by calculating Q (chi-squared). Article quality was assessed using the Chalmers scale to determine if quality affected outcome. Effective inter-rater reliability was determined using Rosenthal's method. Significance was set at P <0.05.

Four studies were included. Data were extracted from all four studies for pain (n = 398), three for urgency (n = 306), two for frequency (n = 160), and one study for nocturia (n = 106). The differences (95% confidence limits) were pain: 16.6% (95% Cl 8%, 25%), NNT = 7; urgency: 13.0% (1.0%, 25%), NNT = 7.5; frequency: 16.7% (2.3%, 31.1%), NNT = 6; nocturia: −1% (−19.8%, 21.8%). P values from homogeneity tests were not significant. Mean quality scores were 63.8%, 48.1 %, 50.4%, and 65.6%, respectively, in the four studies; the effective inter-rater reliability was 0.96. Results did not differ when weighted by quality score.

Pentosan polysulfate is more efficacious than placebo in the treatment of pain, urgency, and frequency associated with interstitial cystitis. Pentosan polysulfate is not significantly different from placebo in treating nocturia associated with interstitial cystitis.