An expanded indication for onabotulinum toxin A (Botox) recently received FDA approval to treat adults with upper limb spasticity, according to a release from Actavis, which recently completed its acquisition of Botox manufacturer Allergan. The expansion now adds two thumb muscles—the flexor pollicis longus, a forearm muscle that flexes the thumb; and the adductor pollicis, a muscle in the hand that adducts the thumb—which increases the maximum dose from 360 to 400 units for the treatment of upper limb spasticity. The FDA also approved increasing the maximum 3-month cumulative dose from 360 to 400 units in adults treated for one or more indications.
Botox is the first and only FDA-approved neurotoxin to relieve stiffness resulting from upper limb spasticity, a debilitating neurological condition that causes muscle stiffness in the wrist, fingers, and thumbs that can occur after a stroke and makes the performance of everyday tasks difficult. The new approval comes on the heels of the therapy’s previous FDA nod in 2010 to treat spasticity in the flexor muscles of the elbow, wrist, and fingers in adults, which often occurs after stroke, traumatic brain injury, or the progression of multiple sclerosis.
The expanded indication for Botox comes as a result of two additional randomized, multicenter, double-blind, placebo-controlled studies evaluating its efficacy and safety in patients with upper limb spasticity. In the first study, 170 patients with upper limb spasticity received a single injection (40 units) of either Botox or a placebo into their thumb flexor muscles. At week 6, those who received Botox showed a significant reduction in their thumb flexor muscle tone of 1.0 Botox versus 0.0 placebo (P < .001), as measured by the modified Ashworth Scale.
In the second study, 109 patients with upper limb spasticity received a single injection of either a lower dose (30 units) or higher dose (40 units) of Botox, or a placebo, into their thumb flexor muscles. The higher dose produced a clinically and statistically significant reduction in thumb flexor muscle tone of 0.5 Botox versus 0.0 placebo (P > .010), as measured by the modified Ashworth Scale.