Rifampicin, INH and Ethambutol

Antituberculosis Preps · Antibacterial/Isonicotinic acid derivative/Rifamycin

Indications

Tuberculosis.

Dosage

Adults & Children: 1 tab/15 kg body wt daily one or two hr before a meal.

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. 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.

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. 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: Reduce dosage in patients with…

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.

Advice to Patient

Take with meals. Do not take within 1 hour of consuming aluminium containing antacids. If a dose is missed, take it as soon as you remember unless it is almost time for the next dose. Do not take double dose. Contact prescriber if there is blurred vision or loss of vision. Complete full course of therapy even if you feel better before completion of course. Avoid wearing soft contact lenses. Take care of oral hygiene. Use toothbrushes, dental floss, and toothpicks with caution. Avoid alcohol during therapy.

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.