Brands, Medical Use, Clinical Data
Drug Category
Dosage Forms
Brands / Synonyms
Aethambutolum; D-Ethambutol; Dadibutol; Diambutol; EMB; Etambutol [INN-Spanish]; Etambutolo [DCIT]; Ethambutol; Ethambutol dihydrochloride; Ethambutol HCL; Ethambutol Hydrochloride; Ethambutol, racemic mixture; Ethambutolum [INN-Latin]; Etibi; Myambutol; Tibutol
Indications
For use, as an adjunct, in the treatment of pulmonary tuberculosis.
Pharmacology
Ethambutol is an oral chemotherapeutic agent which is specifically effective against actively growing microorganisms of the genus Mycobacterium, including M. tuberculosis. Ethambutol inhibits RNA synthesis and decreases tubercle bacilli replication. Nearly all strains of M. tuberculosis and M. kansasii as well as a number of strains of MAC are sensitive to ethambutol.
Mechanism of Action
Ethambutol inhibits arabinosyl transferases involved in cell wall biosynthesis.
Absorption
About 75% to 80% of an orally administered dose of ethambutol is absorbed from the gastrointestinal tract.
Toxicity
The most commonly recognized toxic effect of ethambutol is optic neuropathy, which generally is considered uncommon and reversible in medical literature. Other side effects that have been observed are pruritus, joint pain, gastrointestinal upset, abdominal pain, malaise, headache, dizziness, mental confusion, disorientation, and possible hallucinations.
Biotrnasformation / Drug Metabolism
Hepatic. Up to 15% of administered drug is metabolized to inactive metabolites. The main path of metabolism appears to be an initial oxidation of the alcohol to an aldehydic intermediate, followed by conversion to a dicarboxylic acid.
Contraindications
MYAMBUTOL is contraindicated in patients who are known to be hypersensitive to this drug. It is also
contraindicated in patients with known optic neuritis unless clinical judgment determines that it may be used.
MYAMBUTOL is contraindicated in patients who are unable to appreciate and report visual side effects or changes in
vision (eg, young children, unconscious patients).
Drug Interactions
The results of a study of coadministration of ethambutol (50 mg/kg) with an aluminum hydroxide
containing antacid to 13 patients with tuberculosis showed a reduction of mean serum concentrations and urinary
excretion of ethambutol of approximately 20% and 13%, respectively, suggesting that the oral absorption of ethambutol
may be reduced by these antacid products. It is recommended to avoid concurrent administration of ethambutol with
aluminum hydroxide containing antacids for at least 4 hours following ethambutol administration.
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