Ethambutol

Ethambutol Hydrochloride Tablets, USP are indicated for the treatment of pulmonary tuberculosis. It should not be used as the sole antituberculous drug, but should be used in conjunction with at least one other antituberculous drug. Selection of the companion drug should be based on clinical experience, considerations of comparative safety, and appropriate in vitro susceptibility studies. …

• Ethambutol hydrochloride should not be used alone, in initial treatment or in retreatment
• Ethambutol hydrochloride should be administered on a once every 24-hour basis only
• Absorption is not significantly altered by administration with food
• Therapy, in general, should be continued until bacteriological conversion has become permanent and maximal clinical improvement has occurred
• Ethambutol hydrochloride is not recommended for use
• In pediatric patients under 13 years of age since safe conditions for use have not been established
• Initial Treatment In patients who have not received previous antituberculous therapy, administer ethambutol hydrochloride 15 mg/kg (7 mg/lb) of body weight, as a single oral dose once every 24 hours
• In the more recent studies, isoniazid has been administered concurrently in a single, daily, oral dose
• Retreatment In patients who have received previous antituberculous therapy, administer ethambutol hydrochloride 25 mg/kg (11 mg/lb) of body weight, as a single oral dose once every 24 hours
• Concurrently administer at least one other antituberculous drug to which the organisms have been demonstrated to be susceptible by appropriate in vitro tests
• Suitable drugs usually consist of those not previously used in the treatment of the patient
• After 60 days of ethambutol hydrochloride administration, decrease the dose to 15 mg/kg (7 mg/lb) of body weight, and administer as a single oral dose once every 24 hours
• During the period when a patient is on a daily dose of 25 mg/kg, monthly eye examinations are advised. …

• Ethambutol hydrochloride is not recommended for use
• In pediatric patients under 13 years of age since safe conditions for use have not been established

There are limited data on the use of ethambutol hydrochloride in the elderly. One study of 101 patients, 65 years and older, on multiple drug antituberculosis regimens included 94 patients on ethambutol hydrochloride. No differences in safety or tolerability were observed in these patients compared with that reported in adults in general. …

• Ethambutol hydrochloride 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
• Ethambutol hydrochloride is contraindicated in patients who are unable to appreciate and report visual side effects or changes in vision (e.g., young children, unconscious patients)

The results of a study of coadministration of ethambutol hydrochloride (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.

Ethambutol hydrochloride may produce decreases in visual acuity which appear to be due to optic neuritis. This effect may be related to dose and duration of treatment. This effect is generally reversible when administration of the drug is discontinued promptly. However, irreversible blindness has been reported. (See PRECAUTIONS and ADVERSE REACTIONS ). Liver toxicities including fatalities have been reported (See ADVERSE REACTIONS ). Baseline and periodic assessment of hepatic function should be performed.

Ethambutol hydrochloride may produce decreases in visual acuity, including irreversible blindness, which appear to be due to optic neuritis. Optic neuropathy including optic neuritis or retrobulbar neuritis occurring in association with ethambutol therapy may be characterized by one or more of the following events: decreased visual acuity, scotoma, color blindness, and/or visual defect. These events have also been reported in the absence of a diagnosis of optic or retrobulbar neuritis. Patients should be advised to report promptly to their physician any change in visual acuity. …

Pregnancy Teratogenic Effects: Pregnancy Category C There are no adequate and well-controlled studies in pregnant women. There are reports of ophthalmic abnormalities occurring in infants born to women on antituberculous therapy that included ethambutol hydrochloride. Ethambutol hydrochloride should be used during pregnancy, only if the benefit justifies the potential risk to the fetus. …

Take it when you remember, unless it is nearly time for the next dose. Then skip the missed one. Never take two doses at once to make up for it. Check your leaflet, as some medicines are different.