The FDA review was announced two weeks after the Health Research Group at Public Citizen, an advocacy group, petitioned the agency to increase its warnings about the risks of Botox and Myobloc, the trade name for another botulinum toxin product made by Malvern., Pa.-based Solstice Neurosciences Inc.
On Friday, Public Citizen urged the FDA to require drug makers to send out warning letters to all doctors who use Botox and Myobloc.
"The FDA could -- and should -- do more than send out a press release about their concerns," said Sidney Wolfe, director of the group. "Every doctor who is injecting botulinum toxin needs to know about the dangers of the toxin spreading to other parts of the body."
It was too early to say whether the news would have any effect on sales. The drug accounted for more than $1 billion in sales for Allergan last year, a third of its revenue. Allergan shares closed Friday $63.30, down almost 6%.
Wu, the Los Angeles dermatologist, said there was a lesson in the news for cosmetic Botox users.
"It is a reminder that Botox is still a medical procedure," she said.
"It should be performed by a board-certified doctor in a medical setting -- not in a salon, not in a spa, not in someone's kitchen."
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How Botox is used
The popular injectable drug Botox smooths wrinkles for up to six months by paralyzing nerve endings around muscles.
The drug, which is made from a form of botulism, is available by prescription and also treats a wide variety of other ailments including crossed eyes, sweaty palms, headaches and juvenile cerebral palsy.
The makers say Botox and the less widely used botulinum-toxin-based drug Myobloc are safe when used as approved by the federal government.
On Friday, the government said at least one death and other serious side effects had been linked to botulinum-based drugs but declined to say which ones.
In rare cases, the Food and Drug Administration said, the toxin may have spread beyond the injection site to other parts of the body, resulting in such problems as paralysis of respiratory muscles and difficulty swallowing.
The most serious effects were among children with cerebral palsy who were injected with the drug to halt muscle spasms, a use not approved by regulators.
Caroline Van Hove, a spokeswoman for Botox maker Allergan Inc., said some children with cerebral palsy may have received far larger doses injected into their leg muscles than the doses given adults seeking wrinkle care.