Which reversal agent crosses the placenta slightly and may contribute to fetal bradycardia?

Which reversal agent crosses the placenta slightly and may contribute to fetal bradycardia?

• A. Neostigmine
• B. Glycopyrrolate
• C. Edrophonium
• D. Atropine

Answer: (A)

The key idea is how much these drugs cross the placenta and what effect they have on fetal heart rate. Reversing agents like acetylcholinesterase inhibitors increase acetylcholine at muscarinic receptors, which can slow the heart. To prevent maternal bradycardia, an antimuscarinic is given with them, but placental transfer varies among agents. Neostigmine can cross the placenta to a small extent, so it has the potential to affect the fetal heart and contribute to fetal bradycardia if not countered. The other options either cross the placenta poorly (glycopyrrolate) or have different fetal effects (atropine crosses readily and more commonly causes fetal tachycardia; edrophonium crosses even less and is less likely to cause fetal bradycardia). Therefore, neostigmine is the reversal agent most associated with a slight placental transfer that could contribute to fetal bradycardia.

The key idea is how much these drugs cross the placenta and what effect they have on fetal heart rate. Reversing agents like acetylcholinesterase inhibitors increase acetylcholine at muscarinic receptors, which can slow the heart. To prevent maternal bradycardia, an antimuscarinic is given with them, but placental transfer varies among agents.

Neostigmine can cross the placenta to a small extent, so it has the potential to affect the fetal heart and contribute to fetal bradycardia if not countered. The other options either cross the placenta poorly (glycopyrrolate) or have different fetal effects (atropine crosses readily and more commonly causes fetal tachycardia; edrophonium crosses even less and is less likely to cause fetal bradycardia). Therefore, neostigmine is the reversal agent most associated with a slight placental transfer that could contribute to fetal bradycardia.