Pharmacokinetics of Ketamine Transfer Into Human Milk.

PURPOSE/BACKGROUND: Ketamine is an N -methyl- d -aspartate-antagonistic dissociative anesthetic infused intermittently for off-label management of treatment-resistant depression, acute suicidality, and postpartum depression. Despite the prevalence of postpartum depression nearing upward of 15% of deliveries, almost no research has been done to evaluate its safety during lactation.

METHODS: In this study, human milk samples were released from the InfantRisk Center's Human Milk Biorepository of 4 participants treated with intermittent ketamine infusions (49-378 mg) to determine the levels of the drug and its active norketamine metabolite using liquid chromatography-mass spectrometry.

RESULTS: The absolute infant dose of ketamine from human milk was 0.003 to 0.017 mg/kg per day, and norketamine was 0.005 to 0.018 mg/kg per day. The relative infant dose (RID) for ketamine ranged from 0.34% to 0.57%. The RID for norketamine ranged from 0.29% to 0.95%. There were no reported infant adverse effects.

CONCLUSION: The findings of this study suggest that the transfer of ketamine, as well as its active metabolite, norketamine, into human milk is minimal, as estimated by RIDs less than 1% in all participants. These relative doses are well below standardly accepted safety thresholds.