Which pharmacologic agent is commonly used to induce or augment labor by stimulating uterine contractions?

• A. Oxytocin (Pitocin)
• B. Methotrexate
• C. Terbutaline
• D. Magnesium sulfate

Answer: (A)

Oxytocin stimulates labor by binding to receptors on uterine smooth muscle, increasing intracellular calcium, and producing stronger, more regular contractions. It’s the go‑to medication for starting labor when there’s a medical need and for augmenting labor when contractions aren’t effectively progressing. It’s given by IV with careful titration to achieve regular, adequate contractions and ongoing cervical change, all while closely monitoring the fetal heart rate and uterine activity. The aim is to promote labor progress without causing too-frequent contractions (tachysystole), which can compromise the fetus. If tachysystole occurs, the dose is adjusted and appropriate supportive measures are used. Be aware of potential adverse effects such as fluid retention and hyponatremia with prolonged high-dose use, so fluid balance and electrolytes are monitored as indicated.

The other agents have different purposes: methotrexate is used to treat ectopic pregnancy or other indications involving rapid cell death, not to induce labor; terbutaline is a tocolytic that relaxes the uterus to stop contractions; magnesium sulfate can also act as a tocolytic and is used for seizure prophylaxis in preeclampsia, not to induce labor.