Rifampicin with isoniazid

How it works

Rifampicin inhibits bacterial DNA-dependent RNA polymerase while isoniazid inhibits mycolic acid synthesis in the mycobacterial cell wall, providing complementary bactericidal activity against Mycobacterium tuberculosis.

Prescribing in practice

• Both components are hepatotoxic, so check baseline liver function, monitor during treatment and advise patients to report symptoms suggestive of hepatitis without delay.
• Rifampicin is a potent inducer of hepatic enzymes and reduces the effectiveness of many drugs, including hormonal contraception, warfarin and certain antiretrovirals — review all co-medication.
• Pyridoxine is usually co-prescribed to prevent isoniazid-related peripheral neuropathy, particularly in those at higher risk.

Monitoring

Monitor liver function and clinical symptoms during treatment, with closer attention in patients with pre-existing liver disease, alcohol dependence or other hepatotoxic therapy.

Counselling the patient

• Take as a single daily dose, usually before food, and complete the whole course exactly as directed.
• Rifampicin colours urine and other body fluids orange-red and can stain soft contact lenses.
• Report any nausea, loss of appetite, yellowing of the skin or eyes, or tingling in the hands or feet.

Evidence & guidelines

Combined rifampicin and isoniazid is a standard component of NICE-recommended tuberculosis treatment and certain latent TB infection regimens.