indication

For the treatment of cervical dystonia in adults to decrease the severity of abnormal head position and neck pain associated with cervical dystonia. Also for the treatment of severe primary axillary hyperhidrosis that is inadequately managed with topical agents and for the treatment of strabismus and blepharospasm associated with dystonia, including benign essential blepharospasm or VII nerve disorders in patients 12 years of age and above. Also used cosmetically to temporarily improve the appearance of moderate-to-severe frown lines between the eyebrows (glabellar lines) as well as for the treatment of excessive underarm sweating.

pharmacology

A 150 kDa neurotoxic protein produced from fermentation of Hall strain Clostridium botulinum type A grown in a medium containing casein hydrolysate, glucose and yeast extract. It is purified from the culture solution by dialysis and a series of acid precipitations to a complex consisting of the neurotoxin, and several accessory proteins. Botulinum Toxin Type A is not expected to be present in the peripheral blood at measurable levels following IM or intradermal injection at the recommended doses. The recommended quantities of neurotoxin administered at each treatment session are not expected to result in systemic, overt distant clinical effects, i.e. muscle weakness, in patients without other neuromuscular dysfunction. However, sub-clinical systemic effects have been shown by single-fiber electromyography after IM doses of botulinum toxins appropriate to produce clinically observable local muscle weakness.

mechanism of action

Botulinum Toxin Type A blocks neuromuscular transmission by binding to acceptor sites on motor or sympathetic 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.

toxicity

Based on toxicological studies, it has been estimated that the human LD50 by injection is approximately 2800 Units, equivalent to 28 individual vials of BOTOX (Botulinum Toxin Type A) Purified Neurotoxin Complex (100 Units) for a 70 kg adult. When injected intramuscularly, Botulinum Toxin Type A has been shown to be teratogenic or to have embryocidal effects in some animal species.

absorption

The chemical complexity of Botulinum Toxin Type A combined with its extreme potency limits the opportunity to study its pharmacokinetic profile in humans. Therefore, no human pharmacokinetic studies have been performed. Botulinum Toxin Type A is injected directly into the target organ, a skeletal muscle. Thus, bioavailability of the intravenous or oral route is not of clinical relevance.