Multidrug Therapy: The Pharmacological Basis for Leprosy

Pharmacy
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Leprosy disease, is a chronic granulomatous infection caused by Mycobacterium leprae ,While historically stigmatized, it is now a curable disease thanks to standardized Multi-Drug Therapy (MDT) introduced by WHO in 1981.

Why multiple drugs?
M. leprae has a slow doubling time of 12-14 days and can develop resistance under monotherapy. MDT uses three agents with distinct mechanisms:
1)Rifampicin (600 mg monthly): Bactericidal. Inhibits DNA-dependent RNA polymerase, rapidly eliminating 99.9% of viable bacilli within days.
2)Dapsone (100 mg daily): Bacteriostatic. Competitive inhibitor of dihydropteroate synthase in the folate pathway.
3)Clofazimine (300 mg monthly + 50 mg daily): Weakly bactericidal with anti-inflammatory action. Binds to mycobacterial DNA and increases intracellular oxidants. Also reduces Type 2 lepra reactions.

Regimens:

  1. Paucibacillary (PB) leprosy: Rifampicin + Dapsone for 6 months
  2. Multibacillary (MB) leprosy: All three drugs for 12 months
    Clinical impact:
    Patients become non-infectious within 72 hours of the first rifampicin dose. MDT prevents drug resistance, treats existing infections, and interrupts transmission. Since implementation, global prevalence dropped >95%. Treatment is provided free of charge by WHO.
    Early diagnosis remains key: Hypopigmented anesthetic patches and thickened peripheral nerves are cardinal signs. Leprosy is not highly contagious and is fully curable with MDT.
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India accounts for 50% of the leprosy cases worldwide. Treating and preventing it should be a priority seeing the stigma the patients face.

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Yes. With the above said treatment cure rate is over 98%. WHO recommends single-dose rifampicin (SDR-PEP) for high-risk contacts of patients to prevent transmission.