The Food and Drug Administration said Monday it approved a new warning on Allergan Inc.'s (AGN) Botox and a similar product about the possibility of life-threatening breathing and swallowing problems, following up on an earlier announcement about tougher warnings.

Along with signing off on a boxed warning for Botox and Myobloc, made by Solstice Neurosciences Inc., a private firm in Malvern, Pa., the agency said it was changing the generic names for both products to avoid medication errors. The brand names and product formulations are not changing.

The botulinum toxin drug products are designed to relax block nerve impulses to certain muscles, causing them to relax. They treat cervical dystonia, or uncontrolled muscle contractions of the neck and shoulder muscles, and two products including Botox are approved for cosmetic use to treat wrinkles between the eyebrows.

In April, the FDA had said it would require the agency's toughest boxed warning regarding the risk of adverse events when the effects of the toxin - or the active ingredient used in the products - spread beyond the site where it was injected and a medication guide explaining such risks to patients.

At the time, the agency also approved a similar product, Dysport, with the same boxed warning. Medicis Pharmaceutical Corp. (MRX), Scottsdale, Ariz., markets Dysport in the U.S. to treat frown lines, and Ipsen (IPN.FR), based in Paris, will market the product to treat cervical dystonia.

The strengthened warnings were touched off by reports of breathing problems and a "handful" of deaths in some patients when Botox or Myobloc were being used for an unapproved, off-label use. Most of the deaths and serious problems were reported in children being treated for cerebral palsy-associated limb spasticity. Neither product is approved for such use in the U.S.

The FDA said Monday it had not received "definitive" reports of distant spread of toxin associated with Botox when used at recommended doses for treating frown lines as well as severe underarm sweating, another use for which the product is approved. The agency also said it's not received reports involving distant spread of toxin involving Botox when used at approved doses for eyelid twitches or for crossed eyes.

The FDA said Botox's generic name is onabotulinumtoxinA, after previously being known as Botulinum toxin type A, while Myobloc's name is rimabotulinumtoxinB after previously being called Botulinum toxin type B. Dysport was approved in April with the generic name of abobotulinumtoxinA.

-By Jennifer Corbett Dooren, Dow Jones Newswires; 202-862-9294; jennifer.corbett@dowjones.com