Study: Lower Concentration of PrEP in Pregnant Teens, Young Women


Levels of the HIV pre-exposure prophylaxis (PrEP) drug tenofovir among African adolescent girls and young women were more than 30% lower in those who were pregnant than in those who had recently given birth.

Levels of the HIV pre-exposure prophylaxis (PrEP) drug tenofovir among African adolescent girls and young women were more than 30% lower in those who were pregnant than in those who had recently given birth, according to findings from the National Institutes of Health (NIH)-funded IMPAACT 2009 study.

The 40 study participants took PrEP under direct observation, confirming their near-perfect adherence. PrEP drug levels were lower to a similar degree in the pregnant African adolescent girls and young women compared with American men and non-pregnant, non-lactating women who took PrEP daily under direct observation in an earlier study.

“Adolescent girls and young women in sub-Saharan Africa, including those who are pregnant or have recently given birth, urgently need safe, desirable and effective HIV prevention tools,” said Anthony S. Fauci, MD, director of the National Institute of Allergy and Infectious Diseases (NIAID) at NIH in a press release. “While taking PrEP daily as directed is important for everyone who receives it, these new data suggest daily adherence to PrEP will be especially critical for pregnant adolescents and young women. Additional research is needed to determine the level of protection that daily PrEP can provide this population.”

These findings are from the first phase of the IMPAACT 2009 clinical trial, which was designed to assess whether pregnant and postpartum adolescent girls and young women in southern and eastern Africa are willing and able to consistently take daily PrEP when given enhanced support. Additionally, it would assess whether PrEP is safe for them and their infants.

The investigators measured the concentration of tenofovir in the red blood cells of pregnant and postpartum adolescents, and young women who took PrEP daily or nearly so under the direct observation of a study team member for 12 weeks.

Forty adolescent girls and young women aged 16 to 24 years in Malawi, South Africa, Uganda, and Zimbabwe were a part of the study. Half of the participants were pregnant at 14 to 24 weeks gestation and half had given birth 6 to 12 weeks before enrollment.

The participants collectively took more than 99% of their required PrEP doses daily under direct observation, including in-person and real-time video phone call observations. The PrEP medication used in the study contained both tenofovir and emtricitabine.

Blood samples of the study participants were collected by blotting a drop of blood on filter paper, where it dried, then taking a hole punch of each dried blood spot to measure the concentration of tenofovir. The study team found that the median steady-state concentration of tenofovir was 965 femtomoles (fmol) per punch during pregnancy and 1406 fmol/punch postpartum, which is a 31% difference.

The predicted median steady-state concentrations of tenofovir was similar when investigators used a model that estimates how fast tenofovir is cleared from the blood for each participant. There was a 37% difference, with 890 fmol/punch in pregnancy and 1418 fmol/punch postpartum.

The investigators suggest that daily PrEP may provide substantial protection for pregnant African adolescents and young women as part of a comprehensive HIV prevention program. Based on the available data, the study team believes the drug concentration in the target cells of pregnant adolescents and women who take PrEP daily will fall near this plateau; however, further research would be required.


NIH study finds lower concentration of PrEP drug in pregnant teens & young women. NIH. Published March 9, 2020. Accessed March 19, 2020.

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