Botulinum toxin purified neurotoxin complex (Botox) is a purified form of botulinum toxin type A, produced from a culture of Clostridium botulinum. Injection of botulinum toxin into muscle induces paralysis by inhibiting the release of acetylcholine from motor neurons, thereby blocking neuromuscular conduction. It is approved for the treatment of blepharospasm, strabismus, and excessive sweating. Botox is also approved for use in dermatology to induce paralysis of the muscles of facial expression to reverse deep wrinkles. The effect of an individual treatment usually becomes apparent within 3 days and lasts approximately 3 months. The effect may persist for a longer period after a series of treatments because the muscles atrophy. The major adverse effect is temporary loss of function of a muscle required for normal social functioning, as may occur after inadvertent injection of muscles required for smiling or raising the upper eyelids.
Azelaic acid (Azelex) is a naturally occurring dicar-boxylic acid produced by the yeast Malassezia furfur. Azelaic acid inhibits tyrosinase, a rate-limiting enzyme in the synthesis of the pigment melanin. This may explain why diminution of melanin pigmentation occurs in the skin of some patients with pityriasis versicolor, a disease caused by M. furfur. Azelaic acid is bacteriostatic against a number of species thought to participate in the pathogenesis of acne, including Propionibacterium acnes. The drug may also reduce microcomedo formation by promoting normalization of epidermal keratino-cytes. Azelaic acid is used for the treatment of mild to moderate acne, particularly in cases characterized by marked inflammation-associated hyperpigmentation.
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