Isoniazid Dosing for Tuberculosis Preventive Therapy

Standard Adult Dosing Regimens

The American Thoracic Society recommends administering isoniazid 5 mg/kg (maximum 300 mg) daily for 9 months, or 15 mg/kg (maximum 900 mg) twice weekly under directly observed therapy (DOT), with at least 270 doses required for completion 1, 2
The Centers for Disease Control and Prevention (CDC) requires at least 270 doses over 9 months (up to 12 months if interruptions occur) for daily therapy 3, 4, 5
Completion is based on total doses administered, not duration alone, as recommended by the CDC 3, 4, 5

The American Academy of Pediatrics recommends 10-15 mg/kg daily (maximum 300 mg) for daily therapy in children and adolescents 1, 2
The World Health Organization (WHO) recommends 5 mg/kg up to 300 mg/day for children and adolescents, though others recommend 10 mg/kg 7, 8

The CDC recommends using the same dosing as HIV-negative patients but extending the duration to 12 months minimum for HIV-infected patients 3, 4, 5
The Infectious Diseases Society of America recommends daily isoniazid regimens consisting of at least 270 doses over 9-12 months for HIV-infected patients 3, 4, 5

The Clinical Infectious Diseases society recommends administering pyridoxine (vitamin B6) 25-50 mg daily to all at-risk patients, including pregnant women, breastfeeding infants, and persons with HIV infection 2, 7, 8

The CDC requires monthly assessment of adherence and medication side effects for all patients throughout the entire treatment course 3, 4, 5
The American Thoracic Society recommends monitoring for hepatotoxicity, with asymptomatic aminotransferase elevations occurring in 10-20% of patients, and clinical hepatitis occurring in approximately 0.6% of patients receiving isoniazid alone 1

The CDC recommends performing a medical examination to rule out active TB disease before restarting therapy when it is interrupted for ≥2 months 3, 4, 5
The Infectious Diseases Society of America recommends either continuing the original regimen to complete the recommended total doses or restarting the entire regimen after an interruption 3, 4, 5