indication

For the treatment of lepromatous leprosy, including dapsone-resistant lepromatous leprosy and lepromatous leprosy complicated by erythema nodosum leprosum.

pharmacology

Clofazimine exerts a slow bactericidal effect on Mycobacterium leprae (Hansen's bacillus). Clofazimine inhibits mycobacterial growth and binds preferentially to mycobacterial DNA. Clofazimine also exerts antiinflammatory properties in controlling erythema nodosum leprosum reactions. Clofazimine 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. Measurement of the minimum inhibitory concentration (MIC) of clofazimine 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% clofazimine 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.

mechanism of action

Appears to preferentially bind to mycobacterial DNA leading to disruption of the cell cycle and eventually kills the bacterium. It may also bind to bacterial potassium transporters, thereby inhibiting their function. Lysophospholipids have been found to mediate the activity of this drug.

toxicity

Oral, rabbit: LD₅₀ = 3.3 g/kg; Oral, mouse: LD₅₀ = > 4 g/kg. Severe abdominal symptoms have necessitated exploratory laparotomies in some patients on clofazimine therapy. Rare reports have included splenic infarction, bowel obstruction, and gastrointestinal bleeding. Deaths have been reported, following severe abdominal symptoms.

biotransformation

Hepatic. Three metabolites have been identified - two conjugated and one unconjugated, however, it is not yet known whether these metabolites are pharmacologically active. Metabolite I is formed by hydrolytic dehalogenation of clofazimine, metabolite II presumably is formed by a hydrolytic deamination reaction followed by glucuronidation, and metabolite III appears to be a hydrated clofazimine glucuronide.

absorption

Absorption varies from 45 to 62% following oral administration in leprosy patients. Bioavailability is approximately 70%. Food increases bioavailability and rate of absorption.

half life

10 days following a single dose, 70 days after long-term, high-dose therapy.