Which medication among the following is a calcium channel blocker used as a tocolytic to suppress preterm labor?

Which medication among the following is a calcium channel blocker used as a tocolytic to suppress preterm labor?

• A. Indomethacin
• B. Nifedipine/Procardia
• C. Magnesium sulfate
• D. Terbutaline

Answer: (B)

To relax the uterus in preterm labor, you want a medication that directly reduces uterine smooth muscle contraction by limiting calcium entry. Calcium is essential for muscle contraction; blocking the calcium channels in smooth muscle prevents calcium from entering the cells, lowering intracellular calcium and causing the myometrium to relax. A calcium channel blocker fits this action exactly, so it’s used as a tocolytic to suppress contractions. Among the options, this drug stands out because it works by inhibiting calcium influx, whereas the others work through different mechanisms (indomethacin inhibits prostaglandin synthesis; magnesium sulfate is mainly for seizure prophylaxis with some tocolytic effect via neuromuscular blockade; terbutaline is a beta-adrenergic agonist that relaxes the uterus through another pathway). Use of nifedipine requires monitoring for low blood pressure, since it can cause hypotension, and be cautious with other antihypertensives.

To relax the uterus in preterm labor, you want a medication that directly reduces uterine smooth muscle contraction by limiting calcium entry. Calcium is essential for muscle contraction; blocking the calcium channels in smooth muscle prevents calcium from entering the cells, lowering intracellular calcium and causing the myometrium to relax. A calcium channel blocker fits this action exactly, so it’s used as a tocolytic to suppress contractions. Among the options, this drug stands out because it works by inhibiting calcium influx, whereas the others work through different mechanisms (indomethacin inhibits prostaglandin synthesis; magnesium sulfate is mainly for seizure prophylaxis with some tocolytic effect via neuromuscular blockade; terbutaline is a beta-adrenergic agonist that relaxes the uterus through another pathway). Use of nifedipine requires monitoring for low blood pressure, since it can cause hypotension, and be cautious with other antihypertensives.