Antituberculosis agent (ethylenediamine)
Ethambutol is an antibiotic used to treat pulmonary tuberculosis, always in combination with other antituberculosis drugs. It is important to monitor vision during treatment, because it can affect the optic nerve (blurred vision, colour vision changes).
Also known as: Myambutol
Antacids (aluminium and magnesium) reduce Ethambutol absorption — risk of subtherapeutic levels.
The ethambutol label states that aluminium hydroxide, present in many antacids, reduces ethambutol absorption, potentially lowering plasma concentrations and compromising antituberculosis treatment. Separate ethambutol and antacid administration by at least 4 hours. Adherence and efficacy of the antituberculosis regimen are critical, so this precaution should be passed on to the patient, especially in fixed-dose combination regimens where the schedule is already demanding.
Antacids + ethambutol: aluminium hydroxide reduces ethambutol absorption. Separate administration by at least 4 hours.
Chelation and reduced gastrointestinal absorption.
Clinical TB response; adherence.
Treatment failure.
Separate ethambutol and antacid intake by at least 4 hours.
DailyMed/FDA (NIH/NLM) — approved Ethambutol label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=3f6428d6-3745-4337-ad78-ebfff9f49135 ; approved Antacids label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=c72f0736-ee20-45b4-baf0-b80f1e3fa9cb
Alcohol intake may increase the risk of hepatic adverse effects during antituberculosis treatment.
Limit alcohol intake during treatment.
DailyMed/FDA (NIH/NLM) — approved Ethambutol label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=c12b3482-55f0-4324-bdcd-b129ca2dae73
Ethambutol can be taken with or without food; taking it with food reduces gastrointestinal discomfort.
Take with food if gastric discomfort occurs.
DailyMed/FDA (NIH/NLM) — approved Ethambutol label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=c12b3482-55f0-4324-bdcd-b129ca2dae73
Ethambutol causes dose-dependent optic neuritis; it is contraindicated in patients with prior optic neuritis or unexplained visual changes.
Contraindicated in prior optic neuritis; rule out visual changes before and during treatment.
DailyMed/FDA (NIH/NLM) — approved Ethambutol label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=c12b3482-55f0-4324-bdcd-b129ca2dae73
Ethambutol is renally excreted; in renal impairment accumulation increases the risk of optic neuritis — dose adjustment is required.
Adjust the dose to renal function; monitor visual acuity and colour discrimination.
DailyMed/FDA (NIH/NLM) — approved Ethambutol label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=c12b3482-55f0-4324-bdcd-b129ca2dae73
Ethambutol crosses the placenta; it is not a known teratogen at therapeutic doses and is used in active tuberculosis in pregnancy.
Use in active tuberculosis; the weight-based dose is safe in pregnancy.
Excreted into breast milk; compatible with breastfeeding under supervision.
No specific additional contraception.
DailyMed/FDA (NIH/NLM) — approved Ethambutol label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=c12b3482-55f0-4324-bdcd-b129ca2dae73
Clinical and educational support tool. The information does not replace a medical prescription or the opinion of a qualified healthcare professional.
Bacteriostatic antimycobacterial used in tuberculosis (always in combination); the dose-limiting adverse effect is optic neuritis (dose and duration dependent) — requires ophthalmological surveillance.
Selectively inhibits arabinogalactan synthesis of the mycobacterial cell wall (blocks arabinosyltransferase EmbB), compromising wall integrity; diffuses into macrophages and actively growing bacilli; no cross-resistance with other antimycobacterials.
Well absorbed orally: serum peak 2-5 mcg/mL, 2-4 h after 25 mg/kg; erythrocyte intracellular concentrations ~2x plasma levels; undetectable levels 24 h after the last dose with normal renal function.
Partial metabolism: oxidation of the alcohol group to an aldehydic intermediate and conversion to a dicarboxylic acid; ~50% of the dose excreted unchanged in urine within 24 h and 8-15% as metabolites; 20-22% in faeces; accumulation in renal impairment.
No accumulation with daily 25 mg/kg doses with normal renal function (half-life ~3-4 h with renal elimination); marked accumulation in renal impairment.
Medicines from the same therapeutic group (ATC classification) or the same pharmacological class.
