Botox may be used to treat people with an overactive bladder when other treatments for the conditions have failed, the U.S. Food and Drug Administration announced on Friday.

Overactive bladder is a condition where there are sudden bladder contractions and an urgent need of urination.

Botox is a drug made from a toxin produced by the bacterium Clostridium botulinum, according to Medline Plus. The drug is used in small doses to temporarily remove facial wrinkles, underarm sweating, correct misaligned eyes etc. Botox is manufactured by Allergan Inc. based in Irvine, Calif.

Botox injection can let the muscles of the bladder relax, thus increasing the capacity of the bladder to store urine and reducing urinary incontinence. A procedure called cystoscopy is used to inject Botox in the bladder, FDA said.

"Clinical studies have demonstrated Botox's ability to significantly reduce the frequency of urinary incontinence. Today's approval provides an important additional treatment option for patients with overactive bladder, a condition that affects an estimated 33 million men and women in the United States," said Hylton V. Joffe, M.D., director of the Division of Reproductive and Urologic Products in FDA's Center for Drug Evaluation and Research, in a press release.

The safety of the new treatment was established on clinical tests that included more than 1,000 patients who had an overactive bladder. Study participants either received Botox injections or placebo.

After about 12 weeks, researchers found that patients who received Botox injections had fewer episodes of urine leakage (an average of 1.6 to 1.9 times) than people who got placebo.

FDA said that Botox treatment for overactive bladder can be used when the other treatments for the conditions have failed. Also there should be at least 12 weeks gap between treatments.

Side effects of the treatment included urinary tract infections, pain during urination, urine retention.

Allergen is expected to earn $1.76 billion to $1.8 billion through Botox sales, Reuters Health reported. FDA approval for Botox to treat overactive bladder can add another $200 million per year to Botox sales.