5 (Student Presentation) - Anti tuberculosis: Ethambutol

Question 1

MoA of Ethambutol

Answer 1

Interfere arabinogalactan biosynthesis –> inhibiting arabinosyl transferase –> increase in cell wall permeability

Inhibition of mycolic acid transfer to the cell wall –> accumulation of trehalose monomycolate, trehalose dimycolate, and free mycolic acids –> inhibition of arabinogalactan biosynthesis –> lack of arabian receptors for mycolic acids

Question 2

PK of Ethambutol

Answer 2

Absorption: 80% oral bioavailability, affected by food, antacids, presence of HIV, and age

Distribution: 20 - 30% Protein bound; good tissue distribution, moderate CSF penetration (only 25-50%)

Metabolism: Metabolised by alcohol dehydrogenase

Elimination: Major route –> Renal filtration and active tubular secretion

Question 3

Common side effects

Answer 3

Chills, headache, joint pain, abdominal pain, loss of appetite, nausea and vomitting