The Food and Drug Administration said Tuesday it approved Allergan's botulinum-based drug Botox to treat spasms of the elbow, wrist and fingers.
Botox is most famous for it's ability to smooth frown lines on aging foreheads, but the drug has long been used to treat neck spasms, eye muscle disorders and excessive underarm sweating.
Under the latest FDA indication, Allergan will be able to market Botox as a treatment for adults with spasticity in the flexor muscles of the elbow, wrist, and fingers.
"Muscles affected by spasticity have increased stiffness and tightness, which may lead to pain, difficulties with hygiene and other activities of daily living, and may affect how a patient looks," said Dr. Russell Katz, director of the FDA's division of neurology products.
Allergan, which is based in Irvine, Calif., is studying Botox for a variety of uses, including treating migraine headaches.
Botox works by blocking the connections between nerves and muscle, temporarily paralyzing the spastic muscle. The drug is a purified form of botulinum, one of the most toxic substances in the world.
FDA stressed in a statement that Botox is not approved to treat spasms in larger muscles of the arms or legs. Last year the agency added warnings to Botox about its potential to migrate from limbs to other parts of the body, causing breathing problems.
Companies are prohibited from discussing unapproved drug uses with doctors and patients.
But last year Allergan filed a lawsuit against the FDA challenging that restriction. The company argues it has a First Amendment right to educate doctors about how to safely use Botox to treat limb spasms — even though that use is currently unapproved.
FDA's rules are designed to stop companies from promoting drugs for uses that haven't been federally confirmed as safe and effective. Companies caught promoting drugs for so-called off-label uses can be subject to steep financial penalties.
Last year Pfizer Inc. paid $2.3 billion to settle allegations that it marketed drugs for off-label use.
Preliminary hearings for Allergan's case are scheduled for next month in U.S. District Court for the District of Columbia.
Allergan's shares jumped $2.14, or 3.5 percent, in after-hours trading Tuesday following the FDA's announcement. They ended the regular session down 19 cents at $61.35.