Ethionamide (Trecator) is a derivative of isonicotinic acid and is chemically related to isoniazid. It is a secondary agent used in combination when primary agents are ineffective or contraindicated; it is a bacteriostatic antituberculosis agent. Its exact mechanism of action is unknown but is believed to involve inhibition of oxygen-dependent mycolic acid synthesis. It is thought that mutations in the region of the (inhA) gene that are involved in mycolic acid synthesis can cause both isoni-azid and ethionamide resistance.
Ethionamide is well absorbed following oral administration. It is rapidly and widely distributed to all body tissues and fluids, including the cerebrospinal fluid. Metabolism of ethionamide is extensive, and several di-hydropyridine metabolites are produced. Less than 1% of the drug is eliminated in the urine unchanged.
GI disturbances, including nausea, vomiting, and intense gastric irritation, are frequent. In addition, ethion-amide may cause a wide range of neurological side effects, such as confusion, peripheral neuropathy, psychosis, and seizures. Neurological effects can be minimized by pyridoxine supplementation. Other rare side effects include gynecomastia, impotence, postural hypotension, and menorrhagia.
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