Tuberculosis Dosing Per Kilogram Body Weight
For adults with pulmonary tuberculosis, the recommended daily doses per kilogram body weight are: isoniazid 5 mg/kg (maximum 300 mg), rifampicin 10 mg/kg (maximum 600 mg), pyrazinamide 25 mg/kg (maximum 2000 mg), and ethambutol 15-20 mg/kg (maximum 1600 mg). 1
Standard Daily Dosing Regimen for Adults
The first-line medications follow these weight-based dosing guidelines:
- Isoniazid: 5 mg/kg daily (maximum 300 mg) 1, 2, 3
- Rifampicin: 10 mg/kg daily (maximum 600 mg) 1
- Pyrazinamide: 25 mg/kg daily (maximum 2000 mg) 1
- Ethambutol: 15-20 mg/kg daily (maximum 800-1600 mg depending on body weight) 1, 4
These doses are administered as part of the standard 6-month regimen: 2 months intensive phase with all four drugs, followed by 4 months continuation phase with isoniazid and rifampicin. 1, 2
Intermittent Dosing Options
When directly observed therapy (DOT) is used with intermittent dosing schedules:
Twice-Weekly Dosing
- Isoniazid: 15 mg/kg (maximum 900 mg) 1
- Rifampicin: 10 mg/kg (maximum 600 mg) 1
- Pyrazinamide: 50-70 mg/kg (maximum 3000 mg) 1
- Ethambutol: 50 mg/kg (maximum 2500 mg) 1
Three-Times-Weekly Dosing
- Isoniazid: 15 mg/kg (maximum 900 mg) 1
- Rifampicin: 10 mg/kg (maximum 600 mg) 1
- Pyrazinamide: 50-70 mg/kg (maximum 3000 mg) 1
- Ethambutol: 50 mg/kg (maximum 2500 mg) 1
Pediatric Dosing
Children require higher per-kilogram doses due to different pharmacokinetics:
- Isoniazid: 10-15 mg/kg daily (maximum 300 mg) 1, 2, 3
- Rifampicin: 10-20 mg/kg daily (maximum 600 mg) 1
- Pyrazinamide: 15-30 mg/kg daily (maximum 2000 mg) 1
- Ethambutol: 15-25 mg/kg daily (maximum 2500 mg) 1
For intermittent pediatric dosing, isoniazid increases to 20-40 mg/kg (maximum 900 mg) twice weekly. 1
Critical Dosing Considerations
Maximum Daily Doses
The maximum doses exist to prevent toxicity and should not be exceeded regardless of body weight:
- Isoniazid: 300 mg daily, 900 mg intermittent 1
- Rifampicin: 600 mg 1
- Pyrazinamide: 2000 mg daily, 3000 mg intermittent 1
- Ethambutol: 1600 mg daily, 2500 mg intermittent 1
Genitourinary Tuberculosis
The same weight-based dosing applies for genitourinary TB, with identical intensive and continuation phases as pulmonary disease. 1
Common Pitfall
A critical error is using the daily dose for intermittent regimens. Intermittent dosing requires substantially higher per-kilogram doses (e.g., isoniazid 15 mg/kg vs 5 mg/kg) to maintain therapeutic drug levels. 1 Always verify whether the regimen is daily or intermittent before calculating doses.
Pyridoxine Supplementation
Add pyridoxine 25-50 mg daily with isoniazid for patients at risk of peripheral neuropathy, including pregnant women, HIV-infected patients, diabetics, alcoholics, and malnourished individuals. 2