Placental Drug Transfer — FRCA Primary MCQ

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ModeratePharmacology - General PrinciplesPlacental Drug TransferFRCA Primary

Regarding placental transfer of drugs which factor most promotes transfer?

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Correct answer: E — High lipid solubility and low molecular weight and low protein binding

Drugs cross the placenta by passive diffusion. Factors promoting transfer: low molecular weight (<500 Da) / high lipid solubility / low ionisation at physiological pH / low protein binding. Thiopentone crosses rapidly (high lipid solubility / low MW / 60% unionised). Non-depolarising NMBAs do not cross (quaternary ammonium / highly ionised / high MW).

Reference: Peck Hill Williams 2014 Pharmacology for Anaesthesia and Intensive Care