Ethambutol is an antibiotic used to treat infections caused by mycobacteria, mainly tuberculosis. It works by stopping these bacteria from building a strong cell wall, which helps prevent them from growing and spreading.
This medication is not usually used alone. For tuberculosis, ethambutol is commonly prescribed with other anti-tuberculosis medicines, such as isoniazid, rifampin, and pyrazinamide, because using several medicines together helps treat the infection more effectively and lowers the risk of drug resistance.
Ethambutol should only be taken with medical guidance, as the dose depends on body weight, kidney function, the infection being treated, and the other medicines being used. One of the most important safety concerns is vision changes, which can happen because ethambutol may affect the optic nerve.
Indications
Ethambutol is FDA-approved for the treatment of pulmonary tuberculosis. It is used as part of combination treatment and should not be used as the only medicine for tuberculosis.
In standard treatment for drug-susceptible tuberculosis, ethambutol may be included during the first phase of treatment while drug-susceptibility results are being confirmed. It may be stopped if testing shows that the tuberculosis bacteria are sensitive to key medicines such as isoniazid and rifampin.
Ethambutol may also be used in some treatment plans for nontuberculous mycobacterial infections, such as Mycobacterium avium complex, also called MAC. This use is based on clinical guidance and is usually part of a combination regimen with other antibiotics.
How to take it
Ethambutol is taken by mouth, usually as a tablet. Tablet strengths may include 100 mg and 400 mg, depending on the product and country.
The dose is based on body weight and the reason for treatment. For tuberculosis, common adult dosing in guidelines is about 15 to 25 mg/kg once daily. Some treatment plans may use intermittent dosing, such as 3 times per week, especially in specific clinical situations or when kidney function is reduced.
For pulmonary tuberculosis, ethambutol is usually taken with other tuberculosis medicines. Treatment duration depends on the full regimen, test results, response to treatment, and whether the infection is drug-susceptible or drug-resistant.
Ethambutol can generally be taken with or without food. Taking it with food may help reduce stomach discomfort in some people.
Dosing in kidney disease
Ethambutol is removed from the body partly through the kidneys. People with reduced kidney function may need a lower dose or less frequent dosing.
In some cases, such as severe kidney disease or hemodialysis, ethambutol may be prescribed 3 times per week instead of daily. Kidney function should be considered before and during treatment.
Use in children
Ethambutol dosing in children is also based on body weight. However, extra caution is needed because young children may have trouble noticing or explaining vision changes.
Because of this, the benefits and risks should be carefully assessed, especially in very young children or in children who cannot complete basic vision checks.
Possible side effects
The most important possible side effect of ethambutol is optic neuritis, which is inflammation or damage involving the optic nerve. This can cause blurred vision, reduced visual sharpness, blind spots, or trouble seeing red and green colors.
Vision problems are more likely with higher doses, longer treatment, kidney problems, older age, or pre-existing eye disease. Vision changes may improve after ethambutol is stopped, but some cases can be serious or long-lasting.
Other possible side effects include:
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Nausea
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Vomiting
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Stomach pain
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Loss of appetite
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Headache
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Dizziness
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Joint pain
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Rash or itching
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Fever
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Liver enzyme changes
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Numbness or tingling
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Allergic reactions
Medical care is needed urgently if vision changes occur during treatment. Ethambutol should not be stopped or changed without medical guidance, but new vision symptoms should be reported right away.
Vision monitoring
Vision should usually be checked before starting ethambutol, especially when treatment is expected to last longer than 2 months. Monitoring may include visual acuity testing and color vision testing.
People taking ethambutol should be monitored more closely if they have kidney disease, eye disease, higher doses, or prolonged treatment. Early detection of vision problems is important because stopping the medication early may improve the chance of recovery.
Contraindications
Ethambutol is contraindicated in people with a known allergy or hypersensitivity to ethambutol or any ingredient in the medication.
It is also generally contraindicated in people with known optic neuritis, unless a doctor decides that the benefits outweigh the risks. This is because ethambutol can worsen optic nerve problems and may lead to vision loss.
Ethambutol may not be appropriate for people who cannot recognize or report vision changes, such as very young children or people with certain communication difficulties. In these cases, treatment decisions should be individualized.
Precautions
Ethambutol should be used with caution in people with kidney disease because the medication can build up in the body and increase the risk of side effects. Dose adjustments or less frequent dosing may be needed.
Caution is also needed in people with a history of eye disease, vision problems, or optic nerve conditions. These people may need eye exams before and during treatment.
Some medicines or products may affect how ethambutol is absorbed. Antacids that contain aluminum may reduce ethambutol absorption, so they may need to be separated from ethambutol dosing.