Tocolytics are medications that suppress uterine contractions to delay preterm birth, typically buying about 48 hours to administer antenatal corticosteroids and arrange maternal transport to a facility with the right level of neonatal care. They do not stop labor indefinitely; the goal is to gain time for interventions that improve neonatal outcomes. The nurse must know each agent's mechanism, contraindications, and monitoring, because the safe administration of tocolytics depends on recognizing toxicity and dangerous combinations early. Three agents dominate NCLEX content: indomethacin, nifedipine, and magnesium sulfate. Each works differently, carries distinct adverse effects, and has specific contraindications the nurse must verify before and during administration, so the agent chosen depends heavily on the gestational age and the client's cardiovascular status. Consider a case: you are the nurse caring for a client at 30 weeks in preterm labor receiving magnesium sulfate when you note absent patellar reflexes and a respiratory rate of 10. Which action is the priority? You recognize magnesium toxicity, stop the infusion, prepare calcium gluconate, the antidote, and notify the provider immediately, because respiratory depression and cardiac compromise...