Rifampicin and INH

Antituberculosis Preps · Isonicotinic acid derivative/Rifamycin

Indications

Tuberculosis.

Dosage

Adults: Over 50 kg, 2 cap/tab of 300 mg/150 mg daily; under 50 kg, 3 cap/tab of 150 mg/100 mg daily or 1 cap/tab of 450 mg/300 mg daily. All as a single dose before breakfast. Children: Up to 20 mg/kg daily calculated as rifampicin to be given as a single dose.

Adverse Effects

RIFAMPICIN: Heartburn, epigastric distress, anorexia, nausea, vomiting, diarrhoea, sore mouth. Rash, pruritus, urticaria. Eosinophilia, thrombocytopenia. Muscular weakness, pain in extremities. Visual disturbances, haemoglobinuria, hematuria. Menstrual disturbances. ISONIAZID: Peripheral neuropathy. Nausea, vomiting epigastric distress. Elevated SGOT, SGPT, SGOPT. Agranulocytosis. Fever, skin eruptions, pyridoxine deficiency.

Risk Factor (Pregnancy/Lactation)

Pregnancy: Risk cannot be ruled out. Lactation: Caution advised or effect undetermined. Contraindications: RIFAMPICIN: Previous hypersensitivity to any rifamycin. ISONIAZID: Patients with previous isoniazid associated hepatic injury or other severe adverse reactions with isoniazid. Precautions: RIFAMPICIN: Not recommended for intermittent therapy, caution patients against intentional or accidental interruption of daily dosage regimen, since rare renal hypersensitivity reactions have been reported when therapy is resumed. ISONIAZID: Patients with active chronic liver disease or severe renal dysfunction. Isoniazid crosses the placental barrier and passes into maternal breast milk, observe neonates, breast fed infants of isoniazid treated mothers for any evidence of adverse effects.

Interactions

RIFAMPICIN: Known to induce hepatic microsomal enzymes that metabolize a wide variety of drugs e.g. metoprolol, propranolol, quinidine, corticosteroids, contraceptives, oral anticoagulants, oral sulfonylureas. ISONIAZID: The effectiveness of isoniazid may be decreased when administered with corticosteroid. The effects of benzodiazepines may be increased. The hepatic toxicity of both isoniazid and/or rifampicin may be increased when administered concomitantly.

Advice to Patient

Take atleast 30 minutes before or 2 hours after meals. Do not take aluminium-containing antacids within 1 hour of taking this medication. Vitamin B6 is usually required with this medication, take dose of vitamin B6 as recommended by the prescriber. Complete full course of therapy even if you feel better before completion of course. Keep all doctors and lab appointments.

Pharmacokinetics

RIFAMPICIN: Duration: =24 hrs. Absorption: Oral: Well absorbed; food may delay or slightly reduce peak. Metabolism: Hepatic; undergoes enterohepatic recirculation. Half-life elimination: 3-4 hrs; prolonged with hepatic impairment. End-stage renal disease: 1.8-11 hrs. Time to peak, serum: Oral: 2-4 hrs. Excretion: Faeces (60%-65%). Urine (approx. 30%). ISONIAZID: Absorption: Oral, IM: Rapid and complete; food reduces rate and extent of absorption. Metabolism: Hepatic. Half-life: May be prolonged in patients with impaired hepatic function or severe renal impairment. Fast acetylators: 30-100 mins. Slow acetylators: 2-5 hrs. Time to peak, serum: 1-2 hrs. Excretion: Urine (75%-95%). Small amounts excreted in faeces and saliva.

Compiled by Healify Pharmacy from published drug references. How we compile it →

Always consult a pharmacist or doctor.