Transfer of naltrexone and its metabolite 6,beta-naltrexol into human milk

Abstract

The excretion of naltrexone and its primary metabolite 6,beta-naltrexol in breast milk from a 30-year-old lactating opiate addict undergoing oral naltrexone pharmacotherapy (5 mg/d) was studied. Concentrations of naltrexone and 6,beta-naltrexol in serial milk and plasma samples taken over a 19.3-hour period of a dose interval at steady state were measured by gas chromatography. The calculated infant dose relative to the maternal weight was 0.03% for naltrexone and 0.83% (as naltrexone equivalents) for 6,beta-naltrexol. Total relative infant dose estimated for the complete 24-hour dose interval was 1.06%. Her 6-week-old breastfed infant was healthy, achieving expected milestones, and showed no adverse effects. Only 6,beta-naltrexol was detected in infant plasma and at a very low concentration of 1.1 micro g/L. Use of naltrexone during breastfeeding should be undertaken only after an individual risk benefit analysis.