NIDDK Begins Test of Antidepressant in Painful Bladder Syndrome

Research to Probe Amitriptyline’s Promise

The National Institute of Diabetes and Digestive and Kidney Diseases, or NIDDK, will spearhead a new study aimed at determining whether a 40-year-old antidepressant can help dull painful bladder syndrome, or PBS, and interstitial cystitis, or IC.

NIDDK is funding a 10-center, 270-patient trial designed to compare outcomes in patients who take as many as 75 milligrams daily of amitriptyline with those who receive only a placebo. Unlike earlier NIDDK trials on IC, the amitriptyline research will enroll only newly diagnosed patients who have not yet received therapy.

Smaller studies have suggested that the drug may help block the nerve signals that trigger pain and can reduce the muscle spasms in the bladder associated with pain and frequent urination. The new study is designed to rigorously evaluate those findings.

Crucial Study
“Like so many potential treatments tried before it, amitriptyline looks promising. And we are desperate to find a safe and effective treatment for patients. But until the drug is rigorously tested, we won’t know its true value in these syndromes,” said NIDDK’s Leroy M. Nyberg Jr., Ph.D., M.D.. “And we’ll never know if we are raising false hopes for patients, and unnecessarily spending health care dollars on prescriptions, if we don’t do this study. It’s critical to base our treatment decisions on evidence.”

Amitriptyline is a so-called tricyclic antidepressant. While the drug has been replaced by selective serotonin reuptake inhibitors such as Prozac as a first-line treatment for depression, smaller doses of amitriptyline have been increasingly used for chronic pain syndromes, including fibromyalgia and multiple sclerosis.

Treatments Lacking
Researchers are still searching for effective treatments for IC, which affects about 700,000 people, mostly women. PBS, which includes IC, could account for the pain suffered by as many as 10 million people in the United States. Symptoms include frequent urination and pain as the bladder fills. There is no known cause.

In addition to receiving study medication or placebo, all patients will be instructed in ways to suppress the urge to urinate and diet changes that can reduce the level of bladder irritation. Each patient will be followed from 14 to 26 weeks.

In addition to evaluating the potential of amitriptyline to treat the disorder, the researchers will also collect and analyze patient urine samples as part of an ongoing effort to create a diagnostic test for IC.

NIH Publication No. 06–5743
October 2005