Ethionamide (Eto) or prothionamide (Pto)

Update: January 2022

Forms and strengths

• 250 mg tablet (ethionamide or prothionamide)
• 125 mg dispersible tablet (ethionamide), to be dispersed in 10 ml water

Dosage

• Child and adult: 15 to 20 mg/kg once daily
• Maximum dose: 1000 mg daily

Contra-indications, adverse effects, precautions

• Do not administer to patients with severe hepatic impairment.
• Administer with caution to patients with hepatic disease, diabetes or depression.
• May cause:
  • frequently: gastrointestinal disturbances (abdominal or epigastric pain, diarrhoea, metallic taste, nausea and vomiting, stomatitis, etc.);
  • occasionally: endocrine disorders (gynecomastia, hypothyroidism), alopecia, depression, anxiety, psychosis, seizures, peripheral neuropathy, optic neuritis, hypoglycaemia, vestibular disorders, hepatotoxicity, hypersensitivity reactions.
• For the management of adverse effects, see Appendix 17.
• Avoid or monitor combination with isoniazid or cycloserine or terizidone (increased risk of neurotoxicity) and para-aminosalicylic acid (increased risk of gastrointestinal disturbances and hypothyroidism).
• Administer concomitantly pyridoxine (vitamin B₆); child: 1 to 2 mg/kg (usual range: 10 to 50 mg) once daily; adult: 100 mg once daily.
• Pregnancy: CONTRA-INDICATED
• Breastfeeding: administer pyridoxine to the mother (as above). Observe the breast-fed neonate or infant for adverse effects and supplement it with pyridoxine (1 to 2 mg/kg once daily).

Monitoring

• Symptomatic monitoring.
• Liver function and thyroid function.

Patient instructions

• Take with food and/or at bedtime to limit gastrointestinal disturbances.
• 125 mg tablets should be dispersed in 10 ml water.
• Avoid alcohol during treatment.

Remarks

• To improve tolerance, start with a low dose (e.g. 250 mg daily in adults), then increase over 1 to 2 weeks to achieve the requested dose.
• For the 6HRZEto regimen for drug-susceptible TB meningitis, the dose is 20 mg/kg once daily (max. 750 mg daily).

Storage