– Thiocarlide (isoxyl) is a thiourea derivative that was used in the 1960s to successfully treat tuberculosis (TB). It has considerable antimycobacterial activity in vitro and is effective against multi-drug resistant strains of Mycobacterium tuberculosis in the range of 1-10 &#181g/ml. [1] [2] At concentrations of 10 &#181M, isoxyl inhibits the synthesis of M. bovis during six hours of exposure which is similar to isoniazid (INH) and ethionamide (ETH), two other predominant anti-tuberculosis drugs. Unlike INH and ETH, isoxyl also partially inhibits the synthesis of fatty acids. Isoxyl shows no acute toxicity against primary macrophage cell cultures as demonstrated by diminution of redox activity.[2]