According to animal (sheep) studies, peak maternal/fetal levels of atropine are 8x higher than glycopyrrolate after intravenous maternal administration.
Note that drugs with a MW > 1000 Dalton do not readily cross the placenta, whereas drugs with a MW < 500 Dalton easily cross the placenta unless their they are highly ionized. Atropine (MW 289 Da), glycopyrrolate (MW 398 Da), and scopolamine (MW 303 Da) all have a MW < 500 Da, however glycopyrrolate has a highly polar quaternary ammonium group which prevents it from crossing lipid membranes easily, whereas atropine sulfate and scopolamine hydrobromide are non-polar tertiary amines which penetrate lipid barriers easily. Thus, while there are no human or animal data specifically looking at scopolamine in the placenta, one should assume that scopolamine behaves similarly to atropine.
Placental Transfer of Anticholinergics
- Atropine (MW 289 Da): peak maternal/fetal ratio 1.0 (non-polar tertiary amine)
- Glycopyrrolate (MW 398 Da): peak maternal/fetal ratio 0.13 (highly polar quaternary ammonium group)
- Scopolamine (MW 303 Da): no human/animal data. Non-polar tertiary amine, likely behaves like atropine
References
- S H Murad, K A Conklin, K M Tabsh, C R Brinkman, R Erkkola, B Nuwayhid Atropine and glycopyrrolate: hemodynamic effects and placental transfer in the pregnant ewe. Anesth. Analg.: 1981, 60(10);710-4 PubMed Link
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