The U.S. Food and Drug Administration approved wrinkle-smoothing Botox shots to be used to ease chronic migraine, bringing a potential billion-dollar bonanza to drugmaker Allergan, analysts said.

Ben Andrew, an analyst with William Blair & Co., said the new use could add $1 billion to Allergan's revenues over the next five years, according to the Associated Press.

Irvine, Calif-based Allergan's stock jumped 4.5 percent to reach $71.98 a share during morning trading Monday.

The FDA cleared the drug, made of the toxin botulinum, for adult migraine sufferers who endure the crippling headaches for more than two weeks each month. The drug is not approved for less severe forms of migraine.

Botox could also add around $500 million to its $1.4 billion annual sales if approved to treat overactive bladder disorders next year or in 2012, according to the AP.

The drug, widely used to smooth facial wrinkles, is also approved to treat excessive underarm sweating and eyelid spasms.

In September, the drug giant agreed to a $600 million settlement with the Department of Justice after it was charged with promoting off-label uses of Botox for easing juvenile cerebral palsy, muscle pain and headaches.