Leprosy Treatment Dosing: Fixed-Dose vs Weight-Based Regimens
Leprosy treatment does NOT use mg/kg body weight dosing in standard WHO multidrug therapy (MDT) regimens for adults; instead, fixed doses are used based on age categories. However, pediatric dosing does incorporate weight-based calculations.
Adult Dosing: Fixed-Dose Approach
The World Health Organization recommends fixed-dose regimens for leprosy treatment in adults, not weight-based dosing 1:
- Rifampicin: 600 mg monthly (supervised)
- Dapsone: 100 mg daily (unsupervised)
- Clofazimine: 300 mg monthly (supervised) plus 50 mg daily (unsupervised) 2, 3
These fixed doses apply regardless of adult body weight, which differs fundamentally from many other infectious disease treatments. The WHO Field Trials established these regimens in the early 1980s and they have remained the standard approach 2, 4.
Pediatric Dosing: Weight-Based Calculations
Children require weight-based dosing adjustments. The American Academy of Pediatrics recommends clofazimine at 1-2 mg/kg/day (maximum 100 mg) for pediatric leprosy 1. This represents the primary exception where mg/kg dosing is explicitly used in leprosy treatment.
Alternative Regimens
The monthly rifampin, moxifloxacin, and minocycline (RMM) regimen also uses fixed dosing rather than weight-based calculations 5. This alternative has shown excellent tolerability and completion rates without the skin hyperpigmentation associated with clofazimine 5.
Clinical Rationale for Fixed Dosing
The fixed-dose approach in leprosy differs from weight-based dosing used in leishmaniasis (where miltefosine uses 2.5 mg/kg/day) 6 or other infections. This reflects:
- Simplified field implementation: Fixed doses are easier to administer in resource-limited settings where leprosy is endemic 4, 3
- Proven efficacy: The fixed-dose MDT regimens have demonstrated effectiveness across diverse patient populations without relapse over long-term follow-up (mean 13.7 years) 2
- Logistical advantages: Fixed dosing eliminates the need for precise weight measurements and complex calculations 3
Important Caveats
Clofazimine cannot be split as it comes in 50 mg and 100 mg gelcaps, which limits dose adjustments 1. Dapsone requires screening for G6PD deficiency before initiation due to hemolytic anemia risk, but this doesn't change the fixed 100 mg daily dose 1. Treatment should continue during pregnancy with close monitoring, maintaining the same fixed doses 1.
The distinction between fixed-dose (adult leprosy) and weight-based dosing (pediatric leprosy, leishmaniasis) is critical for proper prescribing and should not be confused across different infectious diseases.