Allergan Inc. gained the most in 19 years on the New York Stock Exchange yesterday after saying its wrinkle-smoother Botox eased migraines, challenging a recommendation by specialists against the product.

The debilitating headaches were briefer in patients who received Botox injections, Allergan, based in Irvine, Calif., said yesterday in a statement reporting on two advanced studies. In May, the American Academy of Neurology issued guidelines based on its conclusion that Botox is ineffective for migraines and less-severe headaches.

Allergan plans to ask the U.S. Food and Drug Administration next year to let it market Botox for the added use, the company said.

An approval may have a limited benefit because many doctors already treat migraines with Botox, said Angela Larson, an analyst with Susquehanna Financial Group in New York. Investors may have overreacted, she said.

"The product has the data to show it reduces the number of days but not necessarily the number of episodes," she said yesterday by phone. "I do not think that the migraine opportunity is a new green field for Botox."

The shares rose $4.92, or 9 percent, to $59.50 in composite trading at 2:59 p.m. An earlier increase of 13 percent, to $61.72, was the biggest since June 21, 1989.

Botox will provide about 30 percent of Allergan's estimated $4.5 billion in sales this year, second only to the company's eye-care products, which generate about 45 percent, Larson said. Breast implants and products for dermatology and obesity will account for about 20 percent, she said.

Doctors are free to treat migraines with Botox, even though the FDA doesn't approve that use. Unless the use is approved, the company cannot promote it, and Allergan disclosed in March that the Justice Department is investigating whether the company improperly promoted Botox for headaches.

Botox is made from botulinum toxin, a poison produced by the bacterium Clostridium botulinum. The injections smooth wrinkles by weakening muscles. It was approved for cosmetic use in 1989.

Allergan said in May, when the American Academy of Neurology issued its guidelines, that the report was "equivocal." The only large studies that could resolve the questions were the company's clinical trials, Allergan said.

Botox injections reduced the duration of migraines and headaches among patients who suffered them 15 or more days a month, the company said.

Botox and Solstice Neurosciences Inc.'s Myobloc are being reviewed by the FDA for a possible link to botulism, the illness caused by the bacteria, the agency said earlier this year.

The agency is evaluating reports of breathing difficulties and death after use of the products by children being treated for arm and leg spasms associated with cerebral palsy, a use not approved by the FDA.