Ethambutol and INH

Antituberculosis Preps · Antibacterial/Isonicotinic acid derivative

Indications

Prophylaxis and treatment of tuberculosis.

Dosage

Adults: Prophylaxis and treatment, 15 mg/kg ethambutol plus 300 mg isoniazid in a single daily dose. Re-treatment, see literature. Children: Not recommended.

Adverse Effects

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. 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: ETHAMBUTOL: Hypersensitivity to ethambutol. Known optic neuritis. ISONIAZID: Patients with previous isoniazid associated hepatic injury or other severe adverse reactions with isoniazid. Precautions: ETHAMBUTOL: Reduce dosage in patients with decreased renal functions. Not recommended in children under thirteen years age. 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

ETHAMBUTOL: The effectiveness may be decreased when taking concomitantly with aluminium salts. 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 on an empty stomach atleast one hour before meals or 2 hours after meals. Swallow whole tablet with water or another drink. Complete full course of treatment even if you are feeling better. If you miss a dose, take it as soon as you remember unless time for the next dose is within 6 hours. Do not take double dose.

Pharmacokinetics

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 hrs. Excretion: Urine (>50%). Faeces (approx. 20%). 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.