Medication (class)	Dosage	Comment	Contraindications and adverse effects	References
Indomethacin (Indocin; class: NSAIDs)	Loading dose: 50 mg rectally or 50 to 100 mg orally Maintenance dosage: 25 to 50 mg orally every four hours for 48 hours Total 24-hour dose should not be greater than 200 mg	NSAIDs theoretically intervene more proximally in the labor cascade than other agents; effectiveness similar to other agents Maternal adverse effect profile is favorable Other NSAIDs (sulindac [Clinoril], ketorolac [formerly Toradol]) may be used May be optimal choice for tocolysis before 32 weeks' gestation	Contraindications: maternal renal or hepatic impairment, active peptic ulcer disease, oligohydramnios Maternal adverse effects: nausea, heartburn Fetal adverse effects: constriction of the ductus arteriosus (not recommended after 32 weeks' gestation), pulmonary hypertension, reversible decrease in renal function with oligohydramnios, intraventricular hemorrhage, hyperbilirubinemia, necrotizing enterocolitis	34, 49, 51–54
Magnesium sulfate	4- to 6-g bolus intravenously over 20 minutes, then 1 to 2 g per hour (3 g per hour maximum)	In widespread use in the United States, although meta-analysis fails to demonstrate improvement in outcomes; comparison studies demonstrate similar effectiveness to other agents in delay of delivery	Contraindication: myasthenia gravis Maternal adverse effects: flushing, lethargy, headache, muscle weakness, diplopia, dry mouth, pulmonary edema, cardiac arrest Newborn adverse effects: lethargy, hypotonia, respiratory depression, demineralization with prolonged use	34, 52, 53, 55, 56
Nifedipine (Procardia; class: calcium channel blockers)	30-mg loading dose orally, then 10 to 20 mg every four to six hours	May offer the best outcomes of the tocolytic agents May prolong pregnancy for seven days; delivery after 34 weeks' gestation is also increased Decreased incidence of neonatal respiratory distress syndrome, necrotizing enterocolitis, intraventricular hemorrhage, and jaundice Neonatal mortality not affected	Contraindication: maternal hypotension Maternal adverse effects: flushing, headache, dizziness, nausea, transient hypotension No fetal adverse effects noted	34, 49, 57
Terbutaline (formerly Brethine; class: beta mimetics)	0.25 mg subcutaneously every 20 to 30 minutes for four to six doses	Appropriate as the first-line agent Beta mimetics may delay delivery for 48 hours, but neonatal outcomes are variable and maternal adverse effects common	Maternal contraindications: heart disease, poorly controlled diabetes mellitus, thyrotoxicosis Maternal adverse effects: cardiac arrhythmias, pulmonary edema, myocardial ischemia, hypotension, tachycardia, hyperglycemia, hyperinsulinemia, hypokalemia, antidiuresis, altered thyroid function, physiologic tremor, palpitations, nervousness, nausea, vomiting, fever, hallucinations Fetal and newborn adverse effects: tachycardia, hypoglycemia, hypocalcemia, hyperbilirubinemia, hypotension, intraventricular hemorrhage	34, 49, 52, 58