How is drug elimination affected during pregnancy regarding GFR?

During pregnancy, particularly in the second and third trimesters, there is a physiological increase in the glomerular filtration rate (GFR). This rise is attributed to several factors, including increased blood volume and cardiac output, which enhance kidney perfusion. As a result, the kidneys are more efficient in filtering blood, leading to a faster elimination of drugs from the body.

This accelerated GFR means that many medications—especially those eliminated by glomerular filtration—may require dosage adjustments during pregnancy to maintain therapeutic efficacy. The increased GFR can be particularly significant for drugs that have a narrow therapeutic index, highlighting the importance of monitoring and adjusting medication dosages as necessary.

The other options do not accurately reflect the changes in GFR during pregnancy. The first trimester does see some changes, but the most significant impact on GFR and drug elimination occurs later in pregnancy, not during the first trimester alone or with a decrease in GFR either. A constant GFR would imply no physiological adaptation, which is not the case as the body undergoes various changes to support the developing fetus.