Transfer of antiretroviral drugs into breastmilk: a prospective study from the Swiss Mother and Child HIV Cohort Study

Introduction In 2018, Switzerland changed its guidelines to support women living with HIV wishing to breastfeed. The exposure of antiretroviral drugs (ARVs) in breastmilk and the ingested daily dose by the breastfed infant are understudied, notably for newer ARVs. This study aimed to quantify ARV concentrations in maternal plasma and breastmilk to determine the milk/plasma ratio, to estimate daily infant ARV dose from breastfeeding and to measure ARV concentrations in infants. Methods All women wishing to breastfeed were included, regardless of their ARV treatment. Breastmilk and maternal plasma samples were mostly collected at mid-dosing interval. Results Twenty-one mother/child pairs were enrolled; of those several were on newer ARVs including 10 raltegravir, 1 bictegravir, 2 rilpivirine, 2 darunavir/ritonavir and 3 tenofovir alafenamide. No vertical HIV transmission was detected (one infant still breastfed). The median milk/plasma ratios were 0.96/0.39 for raltegravir once/twice daily, 0.01 for bictegravir, 1.08 for rilpivirine, 0.12 for darunavir/ritonavir and 4.09 for tenofovir alafenamide. The median estimated infant daily dose (mg/kg) from breastfeeding was 0.02/0.25 for raltegravir once/twice daily, 0.01 for bictegravir, 0.02 for rilpivirine, 0.05 for darunavir/ritonavir and 0.007 for tenofovir alafenamide, resulting in relative infant dose Conclusions ARVs were transferred to a variable extent in breastmilk. Nevertheless, the estimated daily ARV dose from breastfeeding remained low. Differential ARV exposure was observed in breastfed infants with some ARVs being below/above their effective concentrations raising the concern of resistance development if HIV infection occurs. More data on this potential risk are warranted to better support breastfeeding.

Automated summary

This study aimed to quantify antiretroviral drug (ARV) concentrations in maternal plasma and breastmilk, estimate the daily infant dose from breastfeeding, and measure ARV concentrations in infants. The results showed that ARVs were transferred to a variable extent in breastmilk, but the estimated daily ARV dose from breastfeeding remained low. Differential ARV exposure was observed in breastfed infants, raising concerns of resistance development if HIV infection occurs. More research is needed to better support breastfeeding and evaluate the potential risks.