etambutoli

Ethambutol, known in many languages as etambutol, is a first-line antimycobacterial drug used in the treatment of active tuberculosis. It is a bacteriostatic agent that inhibits cell-wall synthesis by blocking arabinosyl transferases required for the production of arabinogalactan, a key component of the mycobacterial cell wall. Ethambutol is typically used in combination with isoniazid, rifampicin, and pyrazinamide during the initial intensive phase of therapy, and may be continued based on susceptibility testing.

Administration and dosing: Ethambutol is given orally in weight-based doses of roughly 15 to 25 mg/kg per day, usually once daily or in two divided doses. In adults, practical daily doses commonly range around 800 mg to 1 g, with adjustments for renal impairment because the drug is largely excreted unchanged in urine.

Pharmacokinetics and interactions: After oral dosing, ethambutol is absorbed well and reaches peak plasma concentrations within a few hours. It is primarily excreted by the kidneys; hepatic metabolism is minimal, so hepatic impairment has limited impact on clearance. There are no major drug interactions with routine anti-TB agents, but concomitant nephrotoxicity or optic toxicity requires monitoring.

Adverse effects and monitoring: The most clinically important adverse effect is dose-related optic neuritis, leading to decreased visual acuity and changes in red–green color vision; this can be irreversible if the drug is continued. Baseline and periodic ophthalmologic examinations are recommended, particularly with higher doses or prolonged therapy. Other adverse effects include headache, dizziness, nausea, rash, and rarely hypersensitivity.

Contraindications and precautions: Ethambutol is contraindicated in hypersensitivity and in patients with optic neuritis. Use with caution in significant renal impairment, with appropriate dose adjustments, and monitor vision during therapy.