About isoniazid
Antituberculosis antibiotic
Used for
- Treats tuberculosis, usually with other medicines.
- Prevents tuberculosis in people at increased risk.
Usual adult dose
Active tuberculosis: usually 5 mg/kg once daily, maximum 300 mg, with other medicines. Prevention: usually 300 mg once daily.
Usual dose in children
Active tuberculosis: usually 10–15 mg/kg once daily, maximum 300 mg. Prevention: usually 10 mg/kg once daily, maximum 300 mg.
Common side effects
- Liver inflammation or damage
- Nausea, vomiting, or abdominal discomfort
- Numbness or tingling in hands and feet
- Rash or fever
Important warnings
- Liver injury can be severe; risk increases with alcohol use.
- Seek urgent assessment for yellow skin, dark urine, or severe tiredness.
- Vitamin B6 may be prescribed to reduce nerve problems.
- Take exactly as prescribed; tuberculosis treatment requires combination therapy.
Pregnancy
Used when needed to treat or prevent tuberculosis; treatment decisions depend on individual risk.
Breastfeeding
Generally compatible with breastfeeding; breastfed infants may need vitamin B6 if the parent takes it.
Interactions
- Can increase effects of warfarin, phenytoin, and some benzodiazepines.
- Rifampicin and pyrazinamide may increase liver injury risk.
- Alcohol increases the risk of liver damage.
- Antacids containing aluminium can reduce absorption; separate administration.
AI-generated from general medical knowledge, not from this product's official leaflet. It may be incomplete or out of date. Not medical advice — ask a pharmacist or doctor before making any decision.