Adult: In combination with other antituberculosis agents in patients with Mycobacterium tuberculosis (M. tuberculosis) resistant to rifampicin or isoniazid, or if there is intolerance to other drugs: 15-20 mg/kg daily as a single daily dose or in 2 divided doses. Max: 1,000 mg daily. Initiate treatment with 250 mg once daily, then gradually titrate to the optimal dose according to patient tolerance. Usual dose: 500-1,000 mg daily. Child: In combination with other antituberculosis agents in patients with M. tuberculosis resistant to rifampicin or isoniazid, or if there is intolerance to other drugs: 10-20 mg/kg daily in 2-3 divided doses. Alternatively, 15 mg/kg once daily. Max: 1,000 mg daily. Dosage recommendations may vary among individual products or between countries (refer to specific product guidelines).
Hepatic Impairment
Severe: Contraindicated.
Administration
Ethionamide Should be taken with food.
Contraindications
Hypersensitivity. Severe hepatic impairment.
Special Precautions
Patient with diabetes mellitus, thyroid dysfunction; depression or other psychiatric illness. Mild to moderate hepatic impairment. Children. Pregnancy and lactation.
Adverse Reactions
Significant: Hepatotoxicity; severe cutaneous adverse reactions (e.g. Stevens-Johnson syndrome, toxic epidermal necrolysis, acute generalised exanthematous pustulosis, drug reaction with eosinophilia and systemic symptoms); reversible hypothyroidism (with or without goitre); psychotic disturbances (e.g. depression), eye disorders (e.g. blurred vision, diplopia, optic neuritis). Blood and lymphatic system disorders: Rarely, purpura and thrombocytopenia. Gastrointestinal disorders: Abdominal pain, diarrhoea, nausea, vomiting, metallic taste, excessive salivation, stomatitis. Hepatobiliary disorders: Hepatitis (with or without jaundice). Immune system disorders: Hypersensitivity reactions. Investigations: Increased serum ALT, AST or bilirubin; weight loss. Metabolism and nutrition disorders: Hypoglycaemia, pellagra-like syndrome, anorexia. Nervous system disorders: Dizziness, drowsiness, headache, restlessness, peripheral neuritis. Reproductive system and breast disorders: Impotence, gynaecomastia. Skin and subcutaneous tissue disorders: Acne vulgaris, photosensitivity, rash. Vascular disorders: Orthostatic hypotension.
Perform culture and susceptibility tests; consult local institutional recommendations before treatment initiation due to antibiotic resistance risks. Monitor LFTs at baseline and every month thereafter; blood glucose and thyroid function tests prior to initiation and periodically during treatment. Perform eye exams (including ophthalmoscopy) at baseline and periodically during treatment. Assess for signs and symptoms of liver problems and severe cutaneous adverse reactions.
Drug Interactions
May increase the serum concentration of isoniazid. May potentiate the toxic effects of other antituberculosis agents. May result in seizures when given with cycloserine.
Food Interaction
May increase the risk of psychotic reaction with alcohol.
Action
Description: Overview: Ethionamide is an isonicotinic acid derivative antituberculosis agent active against mycobacteria, including Mycobacterium tuberculosis. It may exhibit bacteriostatic or bactericidal activity depending on the drug concentration at the infection site and the susceptibility of the infecting organism. Mechanism of Action: The exact mechanism of action is not fully known, but it appears to inhibit peptide synthesis in susceptible organisms. Pharmacodynamics: Resistance to ethionamide develops rapidly if used as monotherapy, but it can be prevented when used in combination with other antituberculosis agents. Cross-resistance between ethionamide and isoniazid has been demonstrated in multidrug-resistant M. tuberculosis strains. However, the majority of M. tuberculosis isolates that are resistant to one drug are usually susceptible to the other drug. Limited data suggest that cross-resistance may occur between ethionamide and thioacetazone. There is no evidence of cross-resistance between ethionamide and streptomycin, cycloserine or aminosalicylic acid. Pharmacokinetics: Absorption: Almost completely absorbed from the gastrointestinal tract. Time to peak plasma concentration: Approx 1 hour. Distribution: Widely distributed into body tissues and fluids, including CSF. Crosses the placenta. Volume of distribution: 93.5 L. Plasma protein binding: Approx 30%. Metabolism: Extensively metabolised in the liver to form ethionamide sulfoxide (active metabolite) and inactive metabolites. Excretion: Via urine (<1% as unchanged drug). Elimination half-life: Approx 2 hours.
Chemical Structure
Ethionamide Source: National Center for Biotechnology Information. PubChem Compound Summary for CID 2761171, Ethionamide. https://pubchem.ncbi.nlm.nih.gov/compound/Ethionamide. Accessed Nov. 26, 2025.
J04AD03 - ethionamide ; Belongs to the class of thiocarbamide derivatives. Used in the systemic treatment of tuberculosis.
References
Brayfield A, Cadart C (eds). Ethionamide. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 10/10/2025.Ethionamide. Gold Standard Drug Database in ClinicalKey [online]. Elsevier Inc. https://www.clinicalkey.com. Accessed 15/10/2025.Ethionamide. UpToDate Lexidrug, AHFS DI (Adult and Pediatric) Online. American Society of Health-System Pharmacists, Inc. Waltham, MA. UpToDate, Inc. https://online.lexi.com. Accessed 10/10/2025.Ethionamide. UpToDate Lexidrug, Lexi-Drugs Multinational Online. Waltham, MA. UpToDate, Inc. https://online.lexi.com. Accessed 10/10/2025.Ethomid Tablets 250 mg (Zulat Pharmacy Sdn. Bhd.). National Pharmaceutical Regulatory Agency - Ministry of Health Malaysia. https://www.npra.gov.my. Accessed 10/10/2025.Trecator Tablet, Film Coated (Wyeth Pharmaceuticals LLC, a subsidiary of Pfizer Inc.). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed. Accessed 10/10/2025.
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