Rifampicin, INH, Ethambutol and Pyrazinamide

Antituberculosis Preps · Antibacterial/Isonicotinic acid derivative/Rifamycin

Indications

Tuberculosis.

Dosage

Adults: All once daily. 30-37 kg, 2 tab; 38-45 kg, 3 tab; 55-70 kg, 4 tab. Children: Not recommended.

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. ETHAMBUTOL: Optic neuritis (related to dose and duration of treatment). Anaphylactoid reactions. Anorexia, nausea, vomiting abdominal distress. Fever, malaise headache dizziness. Elevated serum uric acid level. PYRAZINAMIDE: Hepatitis which can be minimized by dosage adjustment.

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. ETHAMBUTOL: Hypersensitivity to ethambutol. Known optic neuritis. PYRAZINAMIDE: Liver disease. 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. ETHAMBUTOL:…

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: Corticosteroid, benzodiazepine. ETHAMBUTOL: The effectiveness may be decreased when taking concomitantly with aluminium salts. PYRAZINAMIDE: Probenecid, sulfinpyrazone, oral typhoid vaccine.

Advice to Patient

Take 1 hour before or 2 hours after meals with a full glass of water. If there is GI upset, take with meals.

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. ETHAMBUTOL: Absorption: Approx. 80%. Metabolism: Hepatic (20%). Half-life elimination: 2.5-3.6 hrs. End-stage renal disease: 7-15 hrs. Time to peak, serum: 2-4…

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

Always consult a pharmacist or doctor.