The cosmetic effect of BTX-A on wrinkles was originally documented by a plastic surgeon from Sacramento, California, Richard Clark, and published in the journal Plastic and Reconstructive Surgery in 1989. Canadian husband and wife ophthalmologist and dermatologist physicians, JD and JA Carruthers, were the first to publish a study on BTX-A for the treatment of glabellar frown lines in 1992. Similar effects had reportedly been observed by a number of independent groups (Brin, and the Columbia University group under Monte Keen.) After formal trials, on April 12, 2002, the FDA announced regulatory approval of botulinum toxin type A (Botox Cosmetic) to temporarily improve the appearance of moderate-to-severe frown lines between the eyebrows (glabellar lines). Subsequently, cosmetic use of botulinum toxin type A has become widespread. The results of Botox Cosmetic can last up to four months and may vary with each patient. The US Food and Drug Administration approved an alternative product-safety testing method in response to increasing public concern that LD50 testing was required for each batch sold in the market.
After the injection moves from the dermis and into the desired muscle, the nerves there are blocked—rather, their synapses, are blocked—by the Botox. So even though your brain my fire and signal for your body to move a particular muscle, Botox effectively blocks that firing and keeps the muscle from moving. The injected muscle can no longer contract, which causes the wrinkles to relax and soften, and also helps prevent new ones from forming.
As part of the settlement, Allergan agreed to plead guilty to one criminal misdemeanor misbranding charge and pay $375 million. The company acknowledged that its marketing of Botox led to off-label uses of the drug. Allergan also agreed to pay $225 million to resolve civil charges alleging that the marketing of Botox had caused doctors to file false reimbursement claims, though Allergan denied wrongdoing. The company said in a statement that the settlement was in the best interest of its stockholders because it avoided litigation costs and "permits us to focus our time and resources on ... developing new treatments."