Ethionamide

Key facts

• Ethionamide is a second-line antituberculosis drug reserved for tuberculosis that is resistant to standard first-line medicines, always given as part of a multidrug regimen.
• It's taken by mouth, once daily or split into two doses, over many months as part of a longer resistant-TB treatment plan.
• Ethionamide can injure the liver. Blood tests to check liver function are needed before treatment starts and at regular intervals throughout.
• Seek urgent care for yellowing of the skin or eyes, dark urine, or persistent vomiting.

What ethionamide treats

Ethionamide treats multidrug-resistant tuberculosis, used alongside other second-line drugs when the infection does not respond to standard first-line treatment. It is not used as a stand-alone treatment, and it does not treat infections other than tuberculosis.

How ethionamide works

Ethionamide blocks the tuberculosis bacterium from making mycolic acids, the fatty building blocks of its protective cell wall. Without an intact wall, the bacteria become more vulnerable and stop multiplying.

Before you take it

• Ethionamide is teratogenic in animal studies and should be avoided in pregnancy unless there is no safer alternative for resistant TB.
• Tell your doctor about any liver disease, since ethionamide is processed by the liver and can worsen existing damage.
• Report numbness, tingling or burning in the hands or feet. Ethionamide can cause peripheral nerve damage, and your doctor may add vitamin B6 (pyridoxine) to reduce this risk.
• Ethionamide can also affect thyroid function, particularly when combined with another TB drug called para-aminosalicylic acid. Thyroid tests may be part of your monitoring.

Side effects

Common effects include nausea, vomiting, loss of appetite and a metallic taste, which are often dose-limiting early in treatment.

Stop and seek urgent medical care for any of these:

• Yellowing of the skin or eyes, dark urine, or unusual tiredness.
• Persistent vomiting or severe stomach pain.
• Numbness, tingling or burning in the hands or feet.
• Facial swelling, hives, or difficulty breathing.

Safety essentials

• Have liver function tests done before starting ethionamide and at regular intervals during treatment. Stop and contact your doctor if you develop signs of liver problems.
• Take the full course exactly as prescribed alongside your other resistant-TB medicines. Missing doses lets resistant bacteria survive and spread.
• Tell your doctor immediately if you become pregnant or are planning a pregnancy while taking ethionamide.

This page is educational and does not replace advice from a doctor or pharmacist who knows your health history.