Active TB (in conjunction w/ other anti-TB agents)Adult 5 mg/kg once daily. Max: 300 mg. 15 mg/kg twice wkly following 2 mth of daily dosing. Max: 900 mg. Childn 10-20 mg/kg once daily for 6-9 mth or longer. Max: 300 mg. 20-40 mg/kg twice wkly following 2 mth of daily dosing. Max: 900 mg. TB prophylaxisAdult 300 mg once daily for 6-12 mth. Childn 10 mg/kg once daily for 6-12 mth. Max: 300 mg.
Discontinue use at 1st sign of hypersensitivity reaction. Possible optic neuritis; periodic ophthalmoscopic exam is recommended if visual symptoms occur. May prevent & reverse peripheral neuropathy complicating INH use w/ pyridoxine administration. Severe & sometimes fatal hepatitis may develop even after mth of treatment. Elevated serum AST levels. Progressive liver dysfunction. Increased risk of developing hepatitis w/ pre-existing liver disease, increasing age, concurrent use of other hepatotoxic medications & excessive or chronic alcohol use. Instruct patients to immediately report any of the prodromal hepatitis symptoms (eg, fatigue, weakness, malaise, anorexia, nausea or vomiting). Discontinue use & closely follow the patient if symptoms & signs suggestive of hepatic damage are detected; may use alternative agent since continued INH use may cause more severe form of liver damage. Defer preventive treatment in individuals w/ acute hepatic diseases. Restart in very small & gradually increasing doses & immediately w/draw if there is any indication of recurrent liver involvement. Use in absence of a proven or strongly suspected bacterial infection is unlikely to provide benefit to patient & risks development of drug-resistant bacteria. Carefully monitor in patients w/ convulsive disorders, pre-existing hepatic diseases or severe renal dysfunction. Pregnancy & lactation.
Increased conc & toxicity of anticonvulsants (eg, carbamazepine & phenytoin) by inhibiting hepatic metabolism. Decreased GI absorption by Al hydroxide gel; administer INH at least 1 hr before antacid. May increase CNS side effects (eg, dizziness or drowsiness) of cycloserine. Concurrent use w/ disulfiram may lead to coordination difficulties & psychotic episodes. Possible hepatotoxicity w/ rifampin; higher risk in slow INH acetylators, those receiving high doses of INH or w/ pre-existing liver disease. May decrease conc & antifungal effect of ketoconazole. May inhibit metabolism of acetaminophen, corticosteroids, diazepam, oral anticoagulants, primidone & theophylline.
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