Isoniazid | Peripheral neuropathy, hepatitis, rash, mild CNS effects. | AST and ALT; neurologic examination. | Phenytoin (synergistic); disulfiram. | Bactericidal to both extracellular and intracellular organisms. Pyridoxine, 25–50 mg orally daily is given as prophylaxis for neuritis; 50–100 mg orally daily as treatment for it. |
Rifampin | Hepatitis, fever, rash, flu-like illness, gastrointestinal upset, bleeding problems, kidney failure. | CBC, platelets, AST and ALT. | Rifampin inhibits the effect of oral contraceptives, quinidine, corticosteroids, warfarin, methadone, digoxin, oral hypoglycemics; aminosalicylic acid may interfere with absorption of rifampin. Significant interactions with protease inhibitors and nonnucleoside reverse transcriptase inhibitors. | Bactericidal to all populations of organisms. Colors urine and other body secretions orange. May discolor contact lenses. |
Rifapentine | Bone marrow suppression, hematuria/pyuria, hepatitis, gastrointestinal upset, flu-like illness. | CBC, platelets, AST and ALT. | Strong cytochrome P450 inducer with multiple drug interactions. Use in HIV patients receiving antiretroviral therapy should be limited to experts in antiretroviral therapy. | Bactericidal to both extracellular and intracellular organisms. Colors urine and other body secretions orange. Long half-life, can be administered weekly in LTBI prophylaxis. Not for use in induction phase of therapy. |
Pyrazinamide | Hyperuricemia, hepatotoxicity, rash, gastrointestinal upset, joint aches. | Uric acid, AST, ALT. | Rare. | Bactericidal to intracellular organisms. |
Ethambutol | Optic neuritis (reversible with discontinuance of drug; rare at 15 mg/kg); rash. | Red-green color discrimination and visual acuity. | Rare. | Bacteriostatic to both intracellular and extracellular organisms. Mainly used to inhibit development of resistant mutants. Use with caution in kidney disease or when ophthalmologic testing is not feasible. |
Streptomycin | Eighth nerve damage, nephrotoxicity. | Vestibular function (audiograms); BUN and creatinine. | Neuromuscular blocking agents may be potentiated and cause prolonged paralysis. | Bactericidal to extracellular organisms. Use with caution in older patients or those with kidney disease. |