Ethambutol

 

Ethambutol was discovered in 1961. More than forty years later ethambutol continues to be used as part of a standard treatment regimen for TB.

 

Dosage:

Adults:

Adults with liver damage -

creatine clearance < 30 ml/min:

Children:

25 mg/kg daily (max dose 2000 mg)

15 – 25 mg three times per week

25 mg/kg daily (max dose 1200 mg)

Ethambutol should be taken daily during the two month intensive phase of TB treatment. In areas with high isoniazid resistance, ethambutol should be continued during the four month continuation phase.

 

How it works:

Ethambutol is a chemically synthesised bacteriostatic antibiotic. It works against TB by obstructing the formation of the cell wall.

 

Side effects:

Ethambutol can cause retrobular neuritis (inflammation of the optic nerve) characterised by vision impairment. Patients experiencing visual symptoms should receive an eye exam. Vision usually return to normal once the drug is stopped, but permanent damage can occur if the drug is continued.

 

Other common side effects include appetite loss, nausea, vomiting, stomach pain, dizziness and headaches.

Clinical evidence:

Ethambutol was reported to be four times as active as streptomycin in vivo. It was also found to be active against strains that were resistant to isoniazid and streptomycin.1

 

Due to concerns of toxicity in children, a literature review was carried out by the WHO in 2006. The review concluded that In view of the almost total lack of ocular toxicity in children of all ages receiving ethambutol at doses of from 15 – 30 mg/kg documented, it can be recommended that children of all ages can be given ethambutol in daily doses of 20 mg/kg (range 15–25 mg/kg) and three times weekly intermittent doses of 30 mg/kg body weight without undue concern.2

Ethambutol has also been shown to be effective in the treatment of drug resistant TB. Two studies showed that for drug resistant TB patients that are susceptible to pyrazinamide, ethambutol, or streptomyci, the addition of these medicines improves prognosis.3 However, ethambutol should not be included as one of the four main medicines that form the basis of treatment for drug resistant TB.4

 Pricing (per lowest unit, i.e. single tablet or injection):

SA Public sector (Aug 2009 – July 2011 tender)

R (150 mg)/ E (275 mg)/ H (75 mg)/ P (400 mg)

R0.57

SA Public sector (August 2011 – July 2013 tender)

R (150 mg)/ E (275 mg)/ H (75 mg)/ P (400 mg)

R0.47

E (100 mg)

R0.37

E (400 mg)

R0.44

SA Private sector

400 mg

R0.82

* Private sector prices sourced on 26/07/11. Global Drug Facility prices converted to rands on 26/07/11.

* Private and public sector prices may vary between suppliers. The lowest available prices are shown here.

 

Advocacy issues:

Affordable versions of ethambutol are available and supply is secure. Ethambutol is available in fixed dose combinations.

1 RG Wilkerson et al. Stereospecificity in a new type of antituberculosis agent. JACS 83, 2212–2213 (1961).

2 WHO. Ethambutol efficacy and toxicity: literature review and recommendations for daily and intermittent dosage in children. 2006

3 JA Caminero et al. Best drug treatment for multidrug-resistant and extensively drug-resistant tuberculosis. Lancet Infect Dis. 2010 Sep;10(9):621-9.

4 Ibid.

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By Catherine Tomlinson

Published: Aug. 23, 2011, 12:16 p.m.

Last updated: Sept. 7, 2011, 12:31 p.m.

Tags: Treatment

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