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Experimental Drug Targets Overactive Bladder

Mirabegron Is the First Drug in a New Class of OAB Medications
By
WebMD Health News
Reviewed by Laura J. Martin, MD

May 17, 2011 -- An experimental drug may help improve symptoms and quality of life among the estimated 33 million people who live with overactive bladder (OAB).

OAB is marked by frequent urges to urinate, leakage, and the need to make several trips to the bathroom during the night. It is caused by an involuntary contraction of bladder muscle that occurs as the bladder fills up.

Mirabegron is part of a new class of medications that stimulates cells in the bladder's detrusor muscle to facilitate the proper filling and storage of urine in the bladder.

According to new data presented at the annual meeting of the American Urological Association (AUA) in Washington, D.C., people with OAB who took the new drug showed improvements in the number of leaks and frequency of urination when compared with those who took a placebo. People who took mirabegron scored higher on quality-of-life issues across the board compared with people who took a placebo.

Drug manufacturer Astellas Pharma funded the new study and expects to file for FDA approval in the coming months.

Mirabegron Works Differently Than Other OAB Drugs

The new drug may fill an important niche in OAB treatment. Other OAB drugs are part of a class called anticholinergics. They block the nerves that control bladder muscle contractions and allow for relaxation of the bladder smooth muscle.  Side effects of these drugs include dry mouth and constipation.

“All of the treatments that we currently offer work by the same mechanism of action and they all share the same side effects, so when you have a patient in whom anticholinergic medications don’t work or who can’t tolerate them, you have nowhere else to go in the realm of medications,” explains study researcher Victor Nitti, MD, a professor of urology at New York University’s Langone Medical Center in New York City.

“This new class of medication gives us a new way to treat the problem that works by a different mechanism,” he says. The side effect profile is also different. “We don’t see dry mouth or constipation the way we do with anticholinergic drugs.”

The most common side effects seen with mirabegron were headache, high blood pressure, urinary infection, and upper respiratory infections.

After medications, some people with OAB turn to surgery or implantable neuromodulation devices that send mild electrical pulses to the nerve influencing bladder control muscles. Some urologists are also using botulinum toxin injections "off-label" to treat OAB. Off-label refers to drugs that are prescribed for conditions that haven't been approved by the FDA. Behavioral changes including diet changes and pelvic muscle exercises.

AUA spokesman Tomas L. Griebling, MD, MPH, the vice chair of urology at the University of Kansas Medical Center in Kansas City, Kan., tells WebMD that it “is pretty significant to have a new drug in a completely different class.”

He says that “there is very good data to show that significant OAB symptoms have a negative impact on quality of life and can be associated with depression, and [these symptoms] limit social activity, and people don’t go out of home or shopping or to the theater,” he says.  “If they have those problems and if they have tried other therapies that don’t work or developed side effects, this represents another alternative.”

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