Effectiveness of MDT: FAQ
Why is rifampicin given only once a month?
Rifampicin is an exceptionally potent bactericidal agent against M. leprae. A single dose of 600 mg is capable of killing 99.9% or more of viable organisms. However, the rate of killing is not proportionately enhanced by subsequent doses. It is also possible that rifampicin exerts a delayed antibiotic effect for several days, during which the organism is incapable of multiplying. The high bactericidal activity of rifampicin makes a once a month application of the drug feasible and cost-effective for leprosy control programmes.
Why is clofazimine given once a month in addition to the daily dose?
Clofazimine being a repository drug, i.e. it is stored in the body after administration and is then slowly excreted. It is given as a loading dose of 300 mg once a month to ensure that the optimal amount of clofazimine is maintained in the body tissue, even if the patient occasionally misses his or her daily dose.
Can MDT eliminate persisting M. leprae?
The persisting M. leprae are, by definition, those viable organisms which are fully susceptible to the drugs but are surviving despite adequate treatment with anti-leprosy drugs, probably because they are in a low or dormant metabolic state. So far we do not have a drug which can kill these persisting organisms, although rifampicin is known to be capable of killing persisting organisms in another mycobacterial disease, tuberculosis. The evidence so far accumulated showed that persisters, even if they exist, do not play an important role in the occurrence of relapses in leprosy among patients treated with MDT.