isoniazid + rifampicin at a glance
Medicine class
Combination antituberculosis antibiotic
Licensed use
Treatment of all forms of tuberculosis
Food
Take on an empty stomach
Body fluids
Urine, sweat, saliva and tears may become orange-red; soft contact lenses can be permanently stained
What is isoniazid + rifampicin used for?
Used under specialist supervision for tuberculosis.
Licensed for all forms of tuberculosis, including newly diagnosed, advanced and chronic disease.
Some UK TB services use the combination to prevent active disease in selected people with latent tuberculosis infection or significant exposure.
How does isoniazid + rifampicin work?
Rifampicin blocks the bacterial enzyme needed to make RNA and proteins, including in slower-growing tuberculosis bacteria. Isoniazid acts mainly against actively growing bacteria by disrupting formation of their protective cell wall.
isoniazid + rifampicin preparations and strengths
Tablet
Route: Oral
Strengths: 150 mg + 100 mg, 300 mg + 150 mg
How to take isoniazid + rifampicin
Follow the TB team's instructions exactly. Do not stop and restart treatment without advice.
Swallow the coated tablets whole with water.
Take on an empty stomach.
Avoid matured cheeses, cured meats, wine, beer and certain fish if advised because isoniazid can impair tyramine and histamine breakdown.
Tell healthcare professionals before starting any prescription, pharmacy or herbal product.
isoniazid + rifampicin side effects
Common or expected effects
- Feeling or being sick
- Headache or dizziness
- Fever or chills
- Diarrhoea or abdominal discomfort
- Itching or rash
- Tingling or numbness
- Harmless orange-red discolouration of body fluids
Get urgent medical advice
- Liver injury, with loss of appetite, persistent sickness, marked tiredness, upper abdominal pain, dark urine, pale stools or jaundice
- Severe allergy or skin reaction, including blistering, peeling, mouth or eye sores, facial swelling or breathing difficulty
- Unusual bruising, purple spots or bleeding
- New or worsening breathlessness, dry cough or fever
- Kidney problems, including blood in the urine, major changes in urine output or swelling
- Severe watery diarrhoea with fever or weakness
- New seizures, hallucinations, severe confusion, poor balance or loss of coordination
isoniazid + rifampicin in pregnancy
Pregnancy requires prompt review by the TB and maternity teams rather than stopping treatment independently. Human evidence is limited, and the combination should be used only when expected benefit justifies potential fetal risk. Rifampicin near delivery may increase bleeding risk in the mother and newborn, so specialist planning may be needed.
isoniazid + rifampicin while breastfeeding
Rifampicin and isoniazid enter breast milk. Breastfeeding should occur only when the clinician judges that benefits outweigh potential infant risks. Specialist assessment should consider the baby's health and monitoring; pyridoxine may be considered for mother and infant.
isoniazid + rifampicin interactions
Rifampicin strongly induces several enzymes and transporters, while isoniazid inhibits some metabolic pathways. A complete interaction review is essential when treatment starts or stops.
Systemic hormonal contraception
Rifampicin can substantially reduce effectiveness; obtain advice on a suitable non-hormonal method.
Lurasidone and specified hepatitis C or HIV antivirals
Several combinations are contraindicated because rifampicin can reduce exposure enough to cause treatment failure.
Saquinavir with ritonavir
Contraindicated because it increases hepatotoxicity risk.
Common questions about isoniazid + rifampicin
Answers are fully visible for fast scanning and source review.
Why can body fluids turn orange-red?
Rifampicin and its metabolites colour urine and other body fluids. This is expected and usually harmless, although blood in the urine requires assessment.
Can it stain contact lenses?
Yes. Orange-red tears can permanently stain soft contact lenses; ask the eye-care or TB team about alternatives.
Sources
These sources were used to prepare and review this medicine page.
Prepared and reviewed by the iatroX editorial team.