Isoniazid-induced fever.

A 56-year-old man was started on therapy with isoniazid after exhibiting a positive reaction to an intradermal injection of intermediate-strength purified protein derivative of tuberculin. After the first dose and each of the following three doses, nausea, vomiting, chills, and an elevated body temperature ranging from 38 degrees C (100.4 degrees F) to 40 degrees C (104. degrees F) occurred. There was no evidence of a hypersensitivity reaction to isoniazid, such as cutaneous rash, eosinophilia, elevated concentration of IgE, and abnormal results on tests of hepatic function. Following discontinuance of therapy with isoniazid, the temperature returned to normal. This experience illustrates the potential of isoniazid to cause febrile reactions, a situation that could be misdiagnosed as an infectious process.