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Amitriptyline shows limited benefit in treating interstitial cystitis/painful bladder syndrome, data show

Tuesday, May 18 2010 | Comments

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What's This? In treatment-naive patients with interstitial cystitis/painful bladder syndrome, the use of amitriptyline in combination with an education and behavioral modification program did not significantly improve symptoms as compared with placebo, although patients who could tolerate a higher dose did experience significant improvements, according to recently published study results.

Current treatment options for interstitial cystitis/painful bladder syndrome are suboptimal, and while amitriptyline is commonly used to treat the condition, the evidence to support its use is modest, researchers indicated.

To evaluate the effectiveness of the agent for this indication, the investigators conducted a double-blind study in 271 patients with interstitial cystitis/painful bladder syndrome who had not received prior treatment. All patients received a standardized education and behavioral modification program and then were randomized to receive amitriptyline (titrated from 10 mg to 75 mg based on tolerability) or placebo.

A patient-reported global response assessment at 12 weeks was the primary endpoint. Patients were asked to rate their symptoms with one of 7 responses--markedly worse, moderately worse, slightly worse, the same, slightly improved, moderately improved, and markedly improved. Secondary endpoints included assessments for individual symptoms (pain, urgency, frequency, etc.), quality of life, and sexual function.

A global response assessment was provided by 231 patients. On an intent-to-treat basis, there was no statistically significant difference between study groups on the primary endpoint. Specifically, 55% of patients in the amitriptyline group reported they were markedly or moderately improved versus 45% of patients in the placebo group who did so (P=.12).

For the individual symptoms, all outcomes showed greater improvement for amitriptyline as compared with placebo, although the researchers noted the results were generally qualitatively similar between the groups. No difference was seen in study arms for outcomes related to quality of life and sexual function.

When global response assessment was limited to the subgroup of patients who were able to achieve and maintain a daily study drug dose of at least 50 mg, the responder rate was significantly greater in the amitriptyline group than it was in the placebo group (77% vs 53%; P<.001). However, the authors acknowledged that this was not a prespecified analysis and could be subject to numerous biases.

The overall adverse event rate was significantly higher in the amitriptyline arm than it was in the placebo arm (88% vs 72%; P=.0013). Of the five serious adverse events reported, none was classified as being related to the study drug.

The authors noted that the response rate for the placebo group was higher than that seen historically for placebo-treated patients. They suggested this finding could be due to a placebo effect as well as the benefits of the behavioral program.

"Despite our inability to show a beneficial effect of the drug in our primary intent-to-treat analysis, we did observe significant improvement in the global response assessment response rate in subjects who maintained higher doses," they concluded. "Whether this observation accurately reflects the true efficacy of this drug or is a result of bias cannot be determined." (Foster HE, et al. J Urol 2010;183:1853-1858.)

This information concerns a use that has not been approved by the Food and Drug Administration.

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