Drug Groups

approved

Description

A second-line antitubercular agent that inhibits mycolic acid synthesis. It also may be used for treatment of leprosy. (From Smith and Reynard, Textbook of Pharmacology, 1992, p868)

Indication

For use in the treatment of pulmonary and extrapulmonary tuberculosis when other antitubercular drugs have failed.

Pharmacology

Ethinamate is bacteriostatic against M. tuberculosis. In a study examining ethionamide resistance, ethionamide administered orally initially decreased the number of culturable Mycobacterium tuberculosis organisms from the lungs of H37Rv infected mice. Drug resistance developed with continued ethionamide monotherapy, but did not occur when mice received ethionamide in combination with streptomycin or isoniazid.

Toxicity

Symptoms of overdose include convulsions, nausea, and vomiting.

Affected Organisms

Biotransformation

Hepatic and extensive. Metabolized to the active metabolite sulfoxide, and several inactive metabolites. The sulphoxide metabolite has been demonstrated to have antimicrobial activity against Mycobacterium tuberculosis.

Absorption

Essentially completely absorbed following oral administration and not subjected to any appreciable first pass metabolism. Bioavailability approximately 100%.

Half Life

2 to 3 hours

Protein Binding

Approximately 30% bound to proteins.

Elimination

Less than 1% of the oral dose is excreted as ethionamide in urine. Ethionamide is extensively metabolized to active and inactive metabolites.

Distribution

* 93.5 L [healthy volunteers]

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