Type-specific botulinum antitoxins are available as immunoglobins derived from equine and human sources. Various forms of monovalent to pentavalent botulinum antitoxins are available for the various serotypes of clostridium botulinum. Antitoxins may be beneficial for most clinical forms of botulism, but evidence has demonstrated preventive benefits rather than the reversal of clinical manifestations.
The production of antitoxin is complex, requiring almost 2 years to immunize healthy horses against botulinum toxin. The resultant immunoglobulin product, which is then defibrinated, digested, dialyzed, and purified as a 20% protein antitoxin,10 can be lyophilized and preserved.27 Bivalent (serotypes A and B) and serotype E botulinum antitoxin are the equine immunoglobulin preparations available in the United States, the latter as an investigational new drug.9 Whereas the bivalent (AB) preparation is used for patients with presumed wound botulism, both AB and E antitoxins should be administered to patients with foodborne botulism. The trivalent (serotypes A, B, and E) product is no longer available.
Botulinum antitoxin is distributed from the nine regional centers of the Centers for Disease Control and Prevention (CDC) on a named-patient basis after a probable diagnosis of botulism has been established. Each vial of the bivalent botulinum antitoxin contains 7500 IUnits (2381 US units) of type A botulinum antitoxin and 5500 IUnits (1839 US units) of type B antitoxin.2 The type E product contains 5000 IUnits of antitoxin.3 If both are given, each should be administered separately.3
Evidence substantiating the efficacy of types A and E antitoxin is available,17,31 but the efficacy of type B antitoxin has not been established in clinical trials.
Currently, only limited data are available on the relationship of dose and route of administration, the amount of circulating antitoxin found in treated patients, the toxin-neutralizing capacity of this material, and the half-life of the antitoxin. Peak serum concentrations of antitoxin are 10 to 1000 times higher than the concentrations of antitoxin calculated to be necessary to achieve toxin neutralization.14 Ninety percent of the activity of the equine antitoxin administered was detected when all the circulating toxin was neutralized.10,19 The half-lives for antitoxin persistence in a single patient treated with trivalent antitoxin were calculated at 6.5, 7.6, and 5.3 days for antitoxin types A, B, and E, respectively.14 The prolonged half-life of the antitoxin and the exceedingly small quantities of toxin measured explain the limited decrease in antitoxin titers after toxin–antitoxin binding.
In the presence of disease, 1 vial of the antitoxin is administered slowly intravenously (IV) over several minutes as a 1:10 vol/vol dilution in 0.9% sodium chloride solution. Subsequent doses can be given IV every 2 to 4 hours if there is progression of clinical findings.2,3,10,13
For prevention, 20% of a vial of the type A/type B bivalent botulinum antitoxin and 20% of a vial of the type E botulinum antitoxin can ...