Last Updated June 10, 2016
Antimycobacterial agent, synthetic thiocarbamide derivative of isonicotinic acid
250 mg tablets
Indication: used in treatment of multidrug-resistant tuberculosis in combination with other second-line drugs.
Mechanism of action: not precisely defined, appears to inhibit peptide synthesis; may be bacteriostatic or bactericidal depending on concentration.
Pharmacokinetics: Rapidly absorbed and widely distributed in the body; metabolized in liver to active and inactive metabolites; half-life 3 hours. Good penetration of blood–brain barrier.*
Adult Dose: 15-20 mg/kg once daily, maximum 1 g/day; dose may be divided or reduced to improve gastrointestinal tolerance. Should be taken with food to increase gastrointestinal tolerance.*
Use in Renal or Hepatic Insufficiency:
Use in Pregnancy and Breastfeeding: Pregnancy category C. Teratogenicity in animals has been reported. Avoid use in pregnancy.*
Use in Children:
Tuberculosis meningitis in children: 20 mg/kg daily.*
Contraindicated in patients with severe hepatic impairment, porphyria, and those hypersensitive to the drug.
Concomitant administration of pyridoxine may prevent or reduce neurotoxicity.
Use alone or failure to complete full treatment regimen may result in rapid development of resistance.†
Diabetes may be difficult to control after starting this drug.
Ophthalmologic, thyroid function, and laboratory exams (serum transaminases, blood glucose) should be considered before and during therapy.*
Dose may be divided or reduced, or timing of dosage changed to improve gastrointestinal tolerance.
Caution should be used in patients with depression, psychiatric illness, chronic alcoholism, epilepsy, hypothyroidism, and diabetes.
Use alone or failure to complete full treatment regimen may result in rapid development of resistance.‡
Vitamin B6 (pyridoxine) 150 mg can minimise or prevent peripheral neuropathy.
Pellagra-type encephalopathy responds to niacin treatment.
Assess monthly for signs of hypothyroidism, measure thyroid stimulating hormone every 6 months in adults and every 2 months in children.*
Ethionamide has good penetration of blood–brain barrier, so consider using for miliary tuberculosis or tuberculosis meningitis.*
Increased concentration of concomitant medication: isoniazid.
Potentiation of adverse effects of concomitant medication: cycloserine, terizidone (convulsions and other central nervous system toxicity); pyrazinamide (hepatotoxicity and hyperuricemia)*; ethambutol.*
Drug malabsorption may occur with concomitant HIV.†
Diabetes may be difficult to control.
See above for pregnancy and lactation.
Gastrointestinal intolerance (nausea, vomiting, anorexia, metallic taste, abdominal discomfort, diarrhoea, weight loss); central nervous system effects (seizures, pellagra-like encephalopathy, acute psychosis, anxiety and depression, optic neuritis, peripheral neuropathy); hepatotoxicity; hypothyroidism, especially in HIV patients or if used with para-aminosalicylic acid.
Gynaecomastia, impotence, amenorrhoea, hypoglycaemia, hypersensitivity, alopecia, photosensitivity, arthralgia may also occur in rare instances.
*Information from Aurum Institute Drugs on the Go.
†Information from US Prescribing Information.