Ethambutol in pregnancy and breastfeeding


Risk Factor: B
Class: Anti-infectives/ Antituberculosis

Contents of this page:
Fetal Risk Summary
Breast Feeding Summary

Fetal Risk Summary

No reports linking the use of ethambutol with congenital defects have been located. The drug crosses the placenta to the fetus (1,2). In a woman who delivered at 38 weeks’ gestation, ethambutol concentrations in the cord and maternal blood 30 hours after an 800-mg (15 mg/kg) dose were 4.1 and 5.5 ng/mL, respectively, a cord:maternal serum ratio of 0.75 (1). The amniotic fluid ethambutol level was 9.5 ng/mL (1). These levels were within the range (15 ng/mL) required to inhibit the growth of Mycobacterium tuberculosis (1).

The literature supports the safety of ethambutol in combination with isoniazid and rifampin during pregnancy (3,4,5,6 and 7). One investigator studied 38 patients (42 pregnancies) receiving antitubercular therapy (3). The minor abnormalities noted were within the expected frequency of occurrence. Another researcher observed six aborted fetuses at 512 weeks of age (4). Embryonic optic systems were specifically examined and were found to be normal. Most reviewers consider ethambutol, along with isoniazid and rifampin, to be the safest antituberculosis therapy (8,9). However, long-term follow-up examinations for ocular damage have not been reported, causing concern among some clinicians (10).

Breast Feeding Summary

Ethambutol is excreted into human milk. Milk concentrations in two women (unpublished data) were 1.4 g/mL (after an oral dose of 15 mg/kg) and 4.60 g/mL (dosage not given) (11). Corresponding maternal serum levels were 1.5 g/mL and 4.62 g/mL, respectively, indicating milk:serum ratios of approximately 1:1. The American Academy of Pediatrics considers ethambutol to be compatible with breast feeding (12).



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