Pharmacology of botulinum toxin

Background: Botulinum toxin has a well-defined role among dermatologists fo r the treatment of facial wrinkling, brow position, and palmar and axillary hyperhidrosis. Objective: The purpose of this study is to educate dermatologists on the ph armacology of botulinum toxin. Methods: A retrospective review of the literature on botulinum toxin from 1 962 to the present was conducted. We examined the clinical applications of botulinum toxin, cholinergic neuromuscular transmission, the toxin's struct ure and molecular actions, drug and disease interactions at the neuromuscul ar junction, toxin assays, determinants of clinical response, and adverse s ide effects. Results: Botulinum toxin blocks the release of acetylcholine from the presy naptic terminal of the neuromuscular junction. Several drugs and diseases i nterfere with the neuromuscular junction and the effects of botulinum toxin . The mouse bioassay, the most sensitive and specific measurement of toxin activity is the gold standard for botulinum toxin detection and staIlciardi zation. The major determinants of clinical response to treatment are the to xin preparation, individual patient's anatomy, dose and response relationsh ips, length of toxin storage after reconstitution, and immunogenicity. To m inimize potential antibody resistance, one should use the smallest effectiv e dose, utilize treatment intervals of more than 3 months, and avoid booste r injections. Uncommon adverse effects include ptosis, ectropion, diplopia, bruising, eyelid drooping, hematoma formation, and temporary headaches. Conclusion: Botulinum toxin is a safe and effective treatment. Knowledge of the pharmacologic basis of therapy will be useful for standardizing techni ques and achieving consistent therapeutic results in the future.