Isoniazid-induced Flu-like Syndrome: A Rare Side Effect

Drug-induced flu-like syndrome is very rare. It is mainly produced by rifampicin. We report a case of pulmonary tuberculosis (PTB) that developed isoniazid-induced flu-like syndrome, but could be cured with a modified regimen replacing isoniazid with levofloxacin. A 10-year-old girl with PTB was treated with isoniazid (H), rifampicin (R), ethambutol (E), and pyrazinamide (Z). She developed features of flu from the sixth day. Symptoms recurred everyday within 1 h of drug ingestion and subsided automatically by next 12 h. After admission, HREZ were continued. She developed symptoms of flu after 1 h of drug ingestion. Antitubercular therapy (ATT) was stopped and symptoms subsided automatically. Individual drug was started one by one after three days. Severe symptoms of flu developed after taking isoniazid, while other drugs were tolerated well. Levofloxacin was used as an alternative to isoniazid. She was cured after 6 months of chemotherapy. Isoniazid can possibly cause flu-like syndrome and the treating physician should be aware of this possible side effect when using ATT.