Protionamide (or prothionamide) is a drug used in the treatment of tuberculosis; has also been tested for use in the treatment of leprosy. Target: Anti tuberculosis Although ETH and PTH are both potent drugs against M. tuberculosis (MIC = ～0.5 μg/ml) (24), they do not affect E. coli growth, even at very high concentrations (100 μg/ml), which is primarily caused by the absence of an EthA homologue in E. coli [1]. Clinical improvement was noted in 74% of the patients treated with ethionamide and in 83% of those treated with prothionamide. Therapy was well tolerated and drug-related hepatotoxicity did not require discontinuation of therapy. The 500-mg dose of both ethionamide and prothionamide resulted in loss in Mycobacterium leprae viability more rapidly than did the 250-mg dose, and prothionamide at both dose levels was superior to the equivalent dose of ethionamide [2].