General Information

Botox Cosmetic was approved by the FDA in April 2002 for the treatment of moderate to severe glabellar lines (brow furrow) in adult men and women, ages 65 and younger. Botox cosmetic is administered in several injections of purified protein directly into the effected area. The drug works by blocking nerve impulses to relax the contraction of the two major forehead muscles. These contractions are the cause vertical wrinkles between the eyebrows. Following treatment with Botox Cosmetic, improved appearance can be seen as early as one to two days, and the effects can last up to four months.

Botox was previously approved by the FDA for the treatment of several neurological disorders, including strabismus (crossed eyes), blepharospasm (uncontrollable blinking), and head position and neck pain associated with cervical dystonia (a movement disorder characterized by involuntary muscle contractions).

Clinical Results

Botox Cosmetic was tested in a 12-month study consisting of two periods. The first period was a four-month, double-blind, placebo-controlled study of 537 patients with glabellar lines to evaluate efficacy of the drug. At day 30 following treatment, investigators' assessment of the improvement indicated that 80.2% of subjects treated with Botox Cosmetic showed significant reduction in severity of glabellar lines, compared to 3.0% of subjects treated with placebo showing improvement. Patients self-assessment yielded similar results.

The second treatment period was an 8-month, open-label period evaluating the safety of repeated treatments with the drug. 373 subjects from the first period continued into the second period. Of these subjects, 2.1% reported blepharoptosis (droopy eyelid) following the first treatment, and 1.2% reported this effect after a second treatment. 49% of subjects reported side effects of any type.

Mechanism of Action

Botox Cosmetic (botulinum toxin type A) blocks neuromuscular transmission by binding to acceptor sites on motor nerve terminals, entering the nerve terminals, and inhibiting the release of acetylcholine. This inhibition occurs as the neurotoxin cleaves SNAP-25, a protein integral to the successful docking and release of acetylcholine from vesicles situated within nerve endings. When injected intramuscularly at therapeutic doses, Botox Cosmetic produces partial chemical denervation of the muscle resulting in a localized reduction in muscle activity. In addition, the muscle may atrophy, axonal sprouting may occur, and extrajunctional acetylcholine receptors may develop. There is evidence that reinnervation of the muscle may occur, thus slowly reversing muscle denervation produced by Botox Cosmetic. (from Botox prescribing information)