Ethambutol Hydrochloride

Antituberculosis agent.103 106 a

Specific Drugs

Absorption

Bioavailability

75–80% of an oral dose is absorbed from the GI tract;a peak plasma concentrations achieved within 2–4 hours.103 e

Food

Food does not appear to affect absorption.103 e

Special Populations

Serum concentrations are higher in patients with renal impairment.a

Distribution

Extent

Widely distributed into most body tissues and fluids.a Highest concentrations are found in erythrocytes, kidneys, lungs, and saliva; lower drug concentrations are found in ascitic fluid, pleural fluid, brain, and CSF.a

Crosses the placenta and is distributed into cord blood and amniotic fluid.100

Distributed into milk.103

Plasma Protein Binding

8–22%.a

Elimination

Metabolism

Undergoes oxidation in the liver to an aldehyde intermediate which is converted to a dicarboxylic acid derivative.103 e

Elimination Route

Excreted in urine as unchanged drug (50%) and metabolites (8–15%) and in feces as unchanged drug (20–22%).103 e

Removed by peritoneal dialysis and to a lesser extent by hemodialysis.a

Half-life

3.3 hours.a

Special Populations

Half-life prolonged in patients with impaired renal or hepatic function.a Half-life may be ≥7 hours in patients with renal failure.a

• Bacteriostatic in action.a

• Appears to inhibit the synthesis of one or more metabolites in susceptible bacteria resulting in impairment of cellular metabolism, arrest of multiplication, and cell death.103 e

• A highly specific agent; active only against Mycobacterium.103 a Active against M. tuberculosis,a M. avium complex (MAC),a M. bovis,a M. kansasii,107 a g and some strains of M. fortuitum.a Although M. marinum may be susceptible,107 a resistance has been reported.k Active in vitro against M. gordonae,107 M. malmoense,107 and M. smegmatis.107 Has limited activity against M. genavense.107 M. haemophilum107 and some strains of M. xenopi are resistant.107

• Natural and acquired resistance to ethambutol demonstrated in vitro and in vivo in strains of M. tuberculosis.103 a

• No evidence of cross-resistance with other currently available antimycobacterials.103 e

Excipients in commercially available drug preparations may have clinically important effects in some individuals; consult specific product labeling for details.

Please refer to the ASHP Drug Shortages Resource Center for information on shortages of one or more of these preparations.