Lamprene exerts a slow bactericidal effect on Mycobacterium leprae (Hansen's bacillus). Lamprene inhibits mycobacterial growth and binds preferentially to mycobacterial DNA. Lamprene also exerts antiinflammatory properties in controlling erythema nodosum leprosum reactions. However, its precise mechanisms of action are unknown.

Pharmacokinetics

Lamprene has a variable absorption rate in leprosy patients, ranging from 45%-62% after oral administration. The average serum concentrations in leprosy patients treated with 100 mg and 300 mg daily were 0.7 µg/mL and 1.0 µg/mL, respectively. After ingestion of a single dose of 300 mg, elimination of unchanged Lamprene and its metabolites in a 24-hour urine collection was negligible. Lamprene is retained in the human body for a long time. The half-life of Lamprene following repeated oral doses is estimated to be at least 70 days. Part of the ingested drug recovered from the feces may represent excretion via the bile. A small amount is also eliminated in the sputum, sebum, and sweat.

Lamprene is highly lipophilic and tends to be deposited predominantly in fatty tissue and in cells of the reticuloendothelial system. It is taken up by macrophages throughout the body. In autopsies performed on leprosy patients, clofazimine crystals were found predominantly in the mesenteric lymph nodes, adrenals, subcutaneous fat, liver, bile, gall bladder, spleen, small intestine, muscles, bones, and skin.

Microbiology

Measurement of the minimum inhibitory concentration (MIC) of Lamprene against leprosy bacilli in vitro is not yet feasible. In the mouse footpad system, the multiplication of M.leprae is inhibited by introducing 0.0001%- 0.001% Lamprene in the diet. Although bacterial killing may begin shortly after starting the drug, it cannot be measured in biopsy tissues taken from patients for mouse footpad studies until approximately 50 days after the start of therapy.

Lamprene does not wshow cross-resistance with dapsone or rifampin.

The following in vitro data are available, but their clinical significance is unknown. Lamprene has been shown in vitro to inhibit M.avium and M.bovis at concentrations of approximately 0.1-1.0 µg/mL. The MIC for M.avium-intracellulare isolated from patients with acquired immunodeficiency syndrome (AIDS) ranged from 1.0 to 5.0 µg/mL. With a few exceptions, microorganisms other than mycobacteria are not inhibited by Lamprene.

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