Long-term results of amitriptyline treatment for interstitial cystitis

We performed a prospective, open label study to examine the safety and efficacy of the long-term administration of the tricyclic antidepressant amitriptyline in patients with interstitial cystitis (IC).

A total of 94 patients were stratified into 2 groups, namely a National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) group of those who fulfilled NIDDK criteria for IC and a nonNIDDK group of those who presented with characteristic IC symptoms but met at least 1 NIDDK exclusion criterion. Amitriptyline was received strictly at bedtime following an established self-titration protocol without a limitation of the maximum daily dose. Patients reporting improvement in a global response assessment questionnaire were considered treatment responders. Further efficacy measures were changes in pain and urgency, functional bladder capacity and frequency. Changes in the O'Leary-Sant IC index and rating of overall satisfaction with the therapeutic outcome were also reported.

Mean study followup +/- SD was 19.0 +/- 12.5 months. The response rate was 64% (60 patients). The overall mean dose was 55 mg (range 12.5 to 150). Side effects occurred in 79 patients (84%), including dry mouth in 79% and weight gain in 59%. Patient overall satisfaction with the therapeutic result was excellent or good in 43 (46%). The dropout rate was 31% (29 patients) after a mean treatment period of 6 weeks at a mean dose of 70 mg. Nonresponse to treatment was the primary reason for dropout in all cases, while side effects contributed to dropout in 25 (86%). Improvement in the various IC symptoms was statistically significant compared with baseline.

Long-term administration of amitriptyline is a feasible, safe and effective treatment for IC, provided that the drug is used judiciously to minimize adverse effects. The therapeutic response to amitriptyline was uniformly observed in patients fulfilling NIDDK criteria and in those with the pure clinical diagnosis of IC.