The FDA has approved Oxytrol for Women, the first over-the-counter treatment for overactive bladder in women 18 and older.

The condition affects more than 20 million American women, according to Merck, the drug's manufacturer.

Oxytrol helps relax the overactive bladder muscle that leads to symptoms such as the sudden need to urinate and leaking of urine.

It will still only be available in prescription form for men.

Oxytrol for Women is in the form of a patch, applied to the skin every four days, Merck says.

It is expected to hit store shelves by the fall. No cost estimates are yet available, according to Merck.

Oxytrol in pill form by prescription will still be available. Oxytrol for Women contains oxybutynin, a drug that helps to relax the bladder muscle. It belongs to a class of drug called anticholinergics. It is the first of this class to go over-the-counter for overactive bladder treatment.

Each patch delivers 3.9 milligrams of the drug every day.

The FDA approved the drug after reviewing its safety and effectiveness in nine studies involving more than 5,000 women. According to the FDA, the study participants could understand the label information and use the drug appropriately.

Among side effects reported in the studies were skin irritation at the site of the patch, constipation, and dry mouth. Merck will supply an educational leaflet with the product.

Most women who develop overactive bladder are 45 to 60 years old. Many do not seek professional medical help due to embarrassment.

According to the National Association for Continence, those who suffer with bladder problems wait on average seven years before seeking treatment.

Among other prescription medications for the condition are fesoterodine (Toviaz),  solifenacin (Vesicare) and tolterodine (Detrol).

Bladder training and pelvic floor exercises are other common treatment options.

SOURCES:Press release, FDA.Press release, Merck.National Association for Continence: "Seeking Treatment."

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