While Botox is best known for clearing wrinkles by paralyzing facial muscles, the botulin-based drug also is widely used for muscle-spasm conditions. In rare cases, the toxin can spread beyond the injection site to other parts of the body, paralyzing or weakening the muscles used for breathing and swallowing, a potentially fatal side effect. Signs of botulism include difficulty swallowing or breathing, slurred speech and muscle weakness. Those symptoms have been reported as early as several hours after receiving a drug injection.
The agency began investigating the problems last year but is now requiring manufacturers Allergan, Solstice Neurosciences and Medicis to bolster warnings on their products and conduct additional safety studies.
FDA said it received reports of hospitalization and death in children with cerebral palsy taking the drugs for spasticity in their legs. That use is not approved by regulators in the U.S., though it is in some other countries.
The majority of problems seen in adults came after treatment for muscle spasms and cervical dystonia, a type of neck contraction for which the drugs are approved. Some of those patients had to be hospitalized and put on mechanical ventilation in order to breath. While the agency said it has received reports of botulism symptoms in patients taking the drug for anti-wrinkle uses, none of those cases has been confirmed.
Botox and competitors Myobloc from Solstice Neurosciences and Dysport from Medicis will carry a boxed warning, the most serious type the agency enforces.
The new labeling urges physicians to tell patients about the risks of botulin-based drugs and to seek medical care if they develop any symptoms. The companies also will be required to develop medication pamphlets that explain the risks to patients.
Irvine, Calif.-based Allergan said it would cooperate with the agency and stressed that the problems reported by FDA are rare.
"Botox has been marketed in the United States for nearly 20 years, its safety and efficacy profile are well understood, and reports of suspected distant spread have been rare," the company said in a statement.
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