Rifamzide Tablet

Fixed-dose combination of two anti-tuberculosis medicines for:

• Continuation phase of tuberculosis treatment (usually 4 months), after the initial 2-month 4-drug phase
• Part of national TB programme (DOTS) regimens

Adults (by body weight, daily, national TB programme bands): e.g. rifampicin 150 mg + isoniazid 75 mg tablets:

• 25–39 kg: 2 tablets; 40–54 kg: 3 tablets; 55–70 kg: 4 tablets; over 70 kg: 5 tablets — once daily.

Children: paediatric dispersible tablets (rifampicin 75 mg + isoniazid 50 mg) dosed by weight.

• Take on an empty stomach (1 hour before or 2 hours after food), every day at the same time, for the full course.
• Never stop early — incomplete treatment causes drug-resistant TB.
• Pyridoxine (vitamin B6) 10–25 mg daily is often given to prevent nerve damage.

• Acute liver disease, jaundice, or previous severe liver injury from isoniazid
• Allergy to rifamycins or isoniazid
• Use with some HIV protease inhibitors (e.g. saquinavir/ritonavir)

Common: orange-red colour of urine, tears, sweat (harmless; may stain contact lenses), nausea, loss of appetite, stomach upset, tingling or numbness of hands/feet (isoniazid).

Serious: liver damage (hepatitis) — nausea, vomiting, dark urine, yellow eyes; flu-like illness with intermittent dosing; low platelets; severe skin reactions; kidney injury; psychosis or seizures (rare).

• Stop and seek help at once if jaundice, dark urine, persistent vomiting or abdominal pain occur.
• Liver tests before treatment (and during, if risk factors: alcohol, hepatitis B/C, HIV, elderly, pregnancy).
• Avoid alcohol.
• Hormonal contraceptives are less reliable — use a barrier or other method.
• Diabetes, epilepsy, malnutrition: monitor; give pyridoxine.

Used in pregnancy as part of standard TB treatment (benefit outweighs risk); give pyridoxine. Vitamin K may be given to the newborn. Compatible with breastfeeding.

Rifampicin strongly induces liver enzymes — reduces the effect of many drugs:

• Oral contraceptives, warfarin, steroids, sulphonylureas, phenytoin, ketoconazole/fluconazole, methadone, digoxin, antiretrovirals (protease inhibitors, nevirapine), ciclosporin, tacrolimus, calcium-channel blockers, statins
• Isoniazid raises phenytoin and carbamazepine levels
• Antacids reduce isoniazid absorption (take 1 hour apart)
• Paracetamol and alcohol (liver toxicity)

Isoniazid overdose causes vomiting, slurred speech, seizures, metabolic acidosis, coma — emergency (IV pyridoxine is the antidote).

Store below 30°C, protected from light and moisture.