A randomized double-blind trial of oral L-arginine for treatment of interstitial cystitis

Purpose: Nitric oxide synthase activity is decreased in the urine of patien ts with interstitial. cystitis compared to the urine of controls. Ln a prel iminary trial oral L-arginine, the substrate for nitric oxide synthase, inc reased urinary nitric oxide synthase activity and improved interstitial cys titis symptoms. This randomized, double-blind, placebo controlled study fur ther investigates the efficacy of L-arginine treatment for interstitial cys titis. Materials and Methods: A total of 53 interstitial cystitis patients were as signed to receive daily 1,500 mg. L-arginine or placebo orally for 3 months . Interstitial cystitis symptoms were assessed by interviews at 2 weeks, an d 1, 2 and 3 months. Results: The trial was completed by 21 of 27 patients in the L-arginine gro up and 25 of 26 in the placebo group. Using per protocol analysis 29% (6 of 21 patients) in the L-arginine group and 8% (2 of 25) in the placebo group were clinically improved by the end of the trial (p = 0.07). A Likert scal e showed greater global improvement in the L-arginine group (48%, 10 of 21) compared to the placebo group (24%, 6 of 25) at 3 months (p = 0.05) with a decrease in pain intensity (p = 0.04), and tendency toward improvement in urgency (p = 0.06) and frequency of pain (p = 0.09). Using an intention to treat approach to analysis there were no differences between groups. Conclusions: Oral L-arginine (1,500 mg daily) may decrease pain and urgency in a subset of interstitial cystitis patients.