Ethambutol is an antibiotic that eliminates the bacteria that cause tuberculosis (TB). It is generally used in combination with other drugs to treat TB. It can also be given to treat mycobacterium avium complex (MAC) infection.
Antibiotic Class: N-substituted ethylenediamine (Antitubercular Agent.)
Antimicrobial Spectrum: M. tuberculosis and other mycobacteria, including M. avium
Activity against TB
Bacteriostatic inhibitor of cell wall synthesis; bactericidal only at the high end of the dosing range. At doses used over long periods of time, ethambutol protects against further development of resistance.
EMB generally is bacteriostatic at the doses that can be achieved in humans. As such, keeping the serum concentrations above the MIC for the entire dosing interval would be desirable from a theoretical standpoint.
Peak oral absorption occurs 2–4 hours after the dose. Draw a peak serum concentration 2–3 hours after the dose; a second sample 6 hours post-dose could be obtained if there is concern about late absorption and in order to estimate the serum half-life. Peak concentrations of 2– 6 mcg/ml are expected with daily dosing. Intermittent doses of 50 mg/kg can be expected to produce peaks of 4–12 mcg/ml.
Preparation : 100 mg tablets; scored 400 mg tablets; coated 100 mg tablets; coated, scored 400 mg tablets.
Storage: Room temperature.
Dose (all once daily)
- Adults: 15–25 mg/kg/day. Higher doses should be used only during the initial months of therapy. For prolonged therapy, the dose should be closer to 15 mg/kg/day to avoid toxicity. Intermittent dosing at 50 mg/kg thrice or twice weekly can be used.
- Children: 15–25 mg/kg/day; doses closer to 15 mg/kg/day should be used if the drug is used for more than 2 months.
- Renal failure/dialysis: 15–25 mg/kg/dose 3 times weekly (not daily).
- Obesity: For obese patients, base dosing on adjusted weight as follows: Ideal body weight + 40% of excess weight
- Ideal body weight (men): 50 kg plus 2.3 kg/inch over 5 ft
- Ideal body weight (women): 45 kg plus 2.3 kg/inch over 5 ft
- Serum levels may be monitored.
What ADVERSE EFFECTS can this drug cause? What should you do about them?
- Ethambutol can sometimes cause nausea, vomiting, loss of appetite, headaches, dizziness, and confusion. If these effects are bothersome, please call your doctor or pharmacist.
- Rarely, ethambutol can cause temporary vision problems. Your vision may decrease or may become blurry and you may have problems with your color vision. Ideally, your vision should be tested before starting ethambutol and on a regular basis while you are receiving this drug. Please notify your doctor if you detect changes in your vision.
- Ethambutol rarely causes tingling or numbness in the hands and feet. It can also cause joint pain and an increased risk of having gout (uric acid deposits in the joints) if you are already prone to having these problems. Inform your doctor if these symptoms appear.
Your doctor will do regular blood tests to verifyyour blood, your uric acid level, as well as your liver and kidney function. Rarely, an allergic reaction with symptoms such as rash, skin itchiness, and fever may occur. If these effects appear, please contact your doctor.
Use in pregnancy/breastfeeding: Safe in pregnancy; can be used while breastfeeding.
Use in renal disease
Use with caution—cleared by the kidneys; dose adjustment required for renal failure. Increased risk of toxicity with renal failure. If needed for use in the regimen, consider therapeutic drug monitoring.
Use in hepatic disease: Safe in liver disease.
Pre-existing optic neuritis; visual changes on ethambutol Retrobulbar neuritis (dose-related—exacerbated during renal failure).