Responses to tuberculosis therapy may be slow, with symptoms persisting for weeks. Patients who fail to respond appropriately should be carefully assessed for evidence of drug resistance, treatment non-compliance and drug malabsorbtion. The most common drug side effect during therapy for tuberculosis is hepatotoxicity. Isoniazid, rifampin and pyrazinamide are all hepatotoxic, though adverse reactions are more common with isoniazid. Baseline liver function tests should be obtained for all patients beginning treatment, and monthly monitoring is recommended for patients with baseline abnormalities or concomitant liver disease.
Clinical monitoring is appropriate for all other patients.
When evidence of hepatitis develops, all drugs should be stopped until signs and symptoms resolve or improve. Patients should then be rechallenged sequentially with each drug in the regimen and monitored for recurrence. Pyrazinamide frequently causes elevated uric acid levels and may occassionally precipitate gout. Monthly assessment of visual acuity and color discrimination is recommended to identify patients experiencing this toxicity. Drug resistant tuberculosis is increasing in prevalence in the United States and internationally.