Isoniazid Dosing for Tuberculosis Treatment

Adult Dosing Regimens

The American Academy of Family Physicians recommends administering isoniazid 5 mg/kg (maximum 300 mg) daily for active tuberculosis treatment in adults 1
The standard 6-month short-course regimens for pulmonary and most extrapulmonary tuberculosis use 5 mg/kg up to 300 mg once daily 2, 3, 4
Intermittent therapy requires 15 mg/kg up to 900 mg administered 2-3 times weekly under direct observation, providing equivalent efficacy when adherence is assured 1

The British Thoracic Society recommends 5 mg/kg based on pharmacokinetic data showing adequate serum concentrations for pediatric patients 2, 3, 4

For extrapulmonary tuberculosis, the standard 6-month regimen dosing (5 mg/kg daily) is used for most sites, including genitourinary, bone/joint, and disseminated disease 2, 3, 4, 5
TB meningitis requires 12 months of therapy in children and adults, with the same weight-based dosing 5

The American Academy of Family Physicians recommends a total treatment duration of 6 months, with 2 months of isoniazid, rifampin, pyrazinamide, and ethambutol, followed by 4 months of isoniazid and rifampin 1, 2, 3, 4
Completion is based on total doses administered, not duration alone, with daily therapy requiring at least 217 doses over 6 months 1

Pyridoxine supplementation of 25-50 mg daily should be administered to prevent peripheral neuropathy, particularly in pregnant women, breastfeeding infants, HIV-infected patients, malnourished patients, alcoholics, and diabetics 6

Baseline assessment should include liver function tests, serum creatinine, and platelet count in all adults, as well as drug susceptibility testing for isoniazid, rifampin, and ethambutol on initial positive cultures 1
Monthly clinical assessments for adherence and adverse effects are necessary throughout treatment, with regular liver function monitoring required for patients with chronic liver disease, alcoholism, hepatitis B/C, or pregnancy 6, 5