Question 16

Outline the influence of pregnancy on pharmacokinetics.

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College Answer

Most candidates divided the answer into effects on absorption, distribution, metabolism and 
elimination, which is a good way of presenting the answer. However, the good candidates also 
mentioned effects on the foetus due to ion trapping caused by the more acidic foetal blood.
Many candidates forgot to include effect on epidural administration of drugs in pregnancy 
caused by engorged epidural veins during labour. 
Candidates lost marks for omitting the effect of increased cardiac output on the rate of 
distribution of IV drugs to effector sites, the effect of increased hepatic blood flow on drugs with 
high intrinsic clearance, the increased clearance of drugs with renal clearance due to 
increased GFR & renal plasma flow.