Ethambutol

Indications

Ethambutol is used for: Tuberculosis

Adult Dose

Oral Primary treatment of pulmonary and extrapulmonary tuberculosis Adult: Initial 8 wk: 15 mg/kg/day or 30 mg/kg thrice wkly given with isoniazid, rifampicin and pyrazinamide. For patients with history of antimycobacterial therapy: Initial doses: 25 mg/kg/day for 60 days, thereafter reduce to 15 mg/kg/day.

Child Dose

Tuberculosis Child: PO 15–25 mg/kg, max 2.5 g q24h For treatment of drug-resistant tuberculosis: 15-25 mg/kg daily or 50 mg/kg twice wkly. For congenitally acquired tuberculosis: Neonates: 15 mg/kg once daily and >1 mth: 15 mg/kg once daily or 30 mg/kg 3 times wkly for 2 mth initial treatment phase.

Renal Dose

Renal impairment: Dose adjustment may be needed as determined by blood levels of ethambutol.

Administration

Should be taken with food.

Contra Indications

Hypersensitivity; optic neuritis. Lactation.

Precautions

Impaired pre-treatment visual acuity, elderly, children. Perform liver, kidney and visual acuity tests regularly. Caution when assessing visual acuity in patients with cataracts, DM, recurrent eye inflammation to make sure that changes are not due to the underlying causes. Lactation: enters breast milk; use with caution (AAP Committee states "compatible with nursing")

Pregnancy-Lactation

Pregnancy Category: B Lactation: enters breast milk; use with caution (AAP Committee states "compatible with nursing")

Interactions

Delayed or reduced absorption w/ Al hydroxide.

Adverse Effects

Side effects of Ethambutol : Acute gout or hyperuricemia, Abdominal pain, Anaphylaxis, Anorexia, Confusion, disorientation, Fever, Headache, LFT abnormalities, Malaise, Nausea Optic neuritis; symptoms may include decreased acuity, color blindness or visual defects (usually revrsible with discontinuation, though irreversible blindness has been reported) Peripheral neuritis, Pruritis, Rash, Vomiting

Mechanism of Action

Ethambutol interferes with RNA synthesis, causing suppression of Mycobacteria multiplication. It also has bacteriostatic action against M tuberculosis by acting on rapidly growing pathogens in cavity walls and is also effective in slow-growing pathogens. Has some action against atypical opportunistic Mycobacteria e.g. M kansasii, M avium complex (MAC).