Botulinum toxin type B (Myobloc): pharmacology and biochemistry.

Purified toxin complexes have found a niche in the treatment of clinical disorders involving muscle hyperactivity. This report describes the fundamental biochemical properties of the commercially available form of Botulinum Toxin Type B and compares these attributes to the Type A form of the Toxin. Both neurotoxins act to inhibit the release of acetylcholine at the neuromuscular junction, causing muscle paralysis. The different serotypes are structurally and functionally similar; however, specific differences in neuronal acceptor binding sites, intracellular enzymatic sites, and species sensitivities suggest that each serotype is its own unique pharmacologic entity. Data are provided on the biochemical properties and long-term stability of the Type B product, which is uniquely formulated as a liquid product.