When I wrote a year ago about surprising new evidence that Botox and other drugs containing the neurotoxin botulinum could travel from the site of injection to the brain, it wasn't clear whether this posed a threat to patients (the study I described was done on lab animals). But yesterday the Food and Drug Administration announced that the risk was all too real: it will now require Botox, Myobloc and the other botulinum drugs to carry a black box warning—the strongest there is—alerting doctors and patients that the drug can spread to distant parts of the body, posing serious risks such as trouble breathing and swallowing. The FDA is also requiring manufacturers to send doctors a letter warning of the risk.
The action comes in response to a petition from Public Citizen, which in 2008 asked FDA to require both a black box and the warning letters. If I’d had to guess, I would have predicted that FDA would have limited the warnings to non-cosmetic uses of the drugs, since that’s where most of the problems had occurred (botulinum is used to treat cervical dystonia, eyelid spasms and a few other medical conditions in addition to frown lines), especially in unapproved uses such a limb spasticity in kids with cerebral palsy.
But the agency said it found 225 cases in which the drug had migrated beyond the injection site. That was alarming enough to justify the black-box decision, even on cosmetic Botox. As FDA put it, "there is insufficient information to fully characterize the safety profile and potential risk factors for spread of botulinum toxin at this time, given that the mechanism by which spread may occur has not been confirmed. . . . Based on available information, it is not possible to precisely predict the role of injection site, injection technique, or dose in the spread of toxin or severity of the event. Therefore, we are seeking safety labeling changes for the both the dermatologic and neurologic indications."