A new study raises the concern that the popular anti-wrinkle treatment Botox may travel from its injection site into the brain.
For the study, published April 2 in the Journal of Neuroscience, researchers injected botulinum toxin — the active ingredient in Botox — into the whisker muscles of rats.
Researchers then looked at the connected brain areas for signs of the toxin. Within three days of the injection, they found remnants of a protein broken down by the toxin in an area of the brainstem.
The toxin also moved from one hippocampus, which controls long-term memory and spatial navigation, to the hippocampus on the opposite side of the brain, and from the superior colliculus, the part of the brain associated with eye-head coordination, back to the eye.
The study found that brain cell activity was disrupted both where botulinum neurotoxin was injected and in some of the distant-but-connected sites.
The study's author, Matteo Caleo of the Italian National Research Council's Institute of Neuroscience in Pisa, called the finding a concern and noted that the effects of the botulinum injection on the hippocampus were still present six months later.
He said more work is needed to better understand how the toxin spreads along nerves and how to prevent the spread or use it therapeutically.
In February, the Food and Drug Administration warned that Botox and a competitor had been linked to dangerous botulism symptoms in some users, including cases so bad that a few children given the drugs for muscle spasms had died.
Two weeks earlier, the nonprofit organization Public Citizen petitioned the FDA to strengthen warnings to users of Botox and competitor Myobloc, citing 180 reports of U.S. patients suffering fluid in the lungs, difficulty swallowing or pneumonia, which resulted in 16 deaths.
The FDA is probing reports of illnesses in people of all ages who used the drugs for a variety of conditions, including at least one hospitalization of a woman given Botox for forehead wrinkles.