Diphtheria treatment includes which of the following antitoxins (or antitoxin source)?

• A. Diphtheria antitoxin (horse serum)
• B. Penicillin G alone
• C. Amoxicillin-clavulanate
• D. Azithromycin

Answer: (A)

Diphtheria treatment centers on neutralizing the circulating toxin with diphtheria antitoxin derived from horse serum. This antitoxin provides immediate, passive immunity by binding the toxin and preventing it from damaging tissues, which is crucial because toxin effects can progress even while bacteria are still present. Antibiotics such as penicillin G, amoxicillin-clavulanate, or azithromycin are important to eradicate the bacteria and prevent spread, but they do not neutralize the toxin itself, so they aren’t antitoxin sources. The horse-derived antitoxin is used for its high-titer antibodies against the diphtheria toxin, though clinicians monitor for potential hypersensitivity to animal proteins.