Ethambutol Dosing for a 55 kg Female Patient
For a 55 kg female patient, the recommended dose of ethambutol is 800 mg (approximately 15 mg/kg) once daily. 1, 2
Dosing Guidelines
Ethambutol dosing is weight-based and depends on whether the patient is receiving initial treatment or retreatment:
Initial Treatment
- Recommended dose: 15-20 mg/kg once daily 1
- For a 55 kg patient, this translates to 800 mg daily 1, 2
- This falls within the weight band of 40-55 kg according to standard dosing tables 1
Retreatment Cases
- Higher initial dose of 25 mg/kg once daily for the first 60 days 2
- After 60 days, decrease to 15 mg/kg once daily 2
- For a 55 kg patient in retreatment, this would be approximately 1375 mg (rounded to 1400 mg using whole tablets) 2
Administration Considerations
- Ethambutol should be administered once every 24 hours 2
- Can be taken with or without food (absorption is not significantly altered) 2
- Should never be used as monotherapy - must be part of a multi-drug regimen 1, 2
- Fixed-dose combination preparations containing ethambutol may be considered to minimize the risk of inadvertent monotherapy 1
Monitoring Requirements
- Baseline visual acuity testing (Snellen chart) and color discrimination testing (Ishihara tests) before starting treatment 1
- Monthly questioning about visual disturbances (blurred vision, scotomata) 1
- Monthly visual acuity and color discrimination testing for:
- Patients on doses >15-25 mg/kg
- Treatment duration >2 months
- Patients with renal insufficiency 1
- Instruct patient to report any visual changes immediately 1
Important Considerations and Precautions
Renal Function
- Ethambutol is primarily cleared by the kidneys 1
- Dose adjustment required for creatinine clearance <70 ml/minute 1
- For end-stage renal disease: 15-20 mg/kg three times weekly after dialysis 1
Adverse Effects
- Retrobulbar neuritis: Main concern, dose-related with minimal risk at 15 mg/kg daily 1
- Peripheral neuritis: Rare adverse effect 1
- Cutaneous reactions: Occur in 0.2-0.7% of patients 1
Special Populations
- Pregnancy: Considered safe for use 1
- Hepatic disease: Can be used safely without dose adjustment 1
- Children: Use with caution in children <5 years whose visual acuity cannot be monitored 1
Clinical Pearls
- Ethambutol is included in initial treatment regimens primarily to prevent emergence of rifampin resistance when primary isoniazid resistance may be present 1
- Discontinue ethambutol immediately and permanently if there are any signs of visual toxicity 1
- Some research suggests that patients weighing <55 kg may achieve lower drug concentrations than those in higher weight bands 3, 4, but the standard 15 mg/kg dosing remains the guideline recommendation 1, 2