Diphtheria antitoxin is administered via intravenous (IV) infusion or intramuscular (IM) injection, depending on the severity of the disease and the patient's condition. Before administration, a skin test is usually performed to assess for potential allergic reactions to the antitoxin. If the patient has a positive skin test, desensitization procedures may be necessary. The dose of antitoxin varies based on the severity of the infection and the patient's age and weight.