Tocolytic

Tocolytics (also called anti-contraction medications or labor suppressants) are medications used to suppress premature labor (from Greek τόκος tókos, 'childbirth', and λύσις lúsis, 'loosening'). Tocolytic therapy is provided when delivery would result in premature birth, postponing delivery long enough for the administration of glucocorticoids, which accelerate fetal lung maturity but may take one to two days before its effects are seen. Tocolytics (also called anti-contraction medications or labor suppressants) are medications used to suppress premature labor (from Greek τόκος tókos, 'childbirth', and λύσις lúsis, 'loosening'). Tocolytic therapy is provided when delivery would result in premature birth, postponing delivery long enough for the administration of glucocorticoids, which accelerate fetal lung maturity but may take one to two days before its effects are seen. The suppression of contractions is often only partial and tocolytics can only be relied on to delay birth for several days. Depending on the tocolytic used the mother or fetus may require monitoring (e.g., blood pressure monitoring when nifedipine is used as it reduces blood pressure; cardiotocography to assess fetal well-being). In any case, the risk of preterm labor alone justifies hospitalization. There is no clear first-line tocolytic agent. Various types of agents are used, with varying success rates and side effects. Some medications are not specifically approved by the U.S. Food and Drug Administration (FDA) for use in stopping uterine contractions in preterm labor, instead being used off-label. Calcium-channel blockers (such as nifedipine) and oxytocin antagonists (such as atosiban) may delay delivery by 2 to 7 days, depending on how quickly the medication is administered. Otherwise, tocolysis is rarely successful beyond 24 to 48 hours because current medications do not alter the fundamentals of labor activation. However, postponing premature delivery by 48 hours appears sufficient to allow pregnant women to be transferred to a center specialized for management of preterm deliveries, and thus give administered corticosteroids the possibility to reduce neonatal organ immaturity. The efficacy of β-adrenergic agonists, atosiban, and indomethacin is a decreased odds ratio (OR) of delivery within 24 hours of 0.54 (95% confidence interval (CI): 0.32-0.91) and 0.47 within 48 hours (OR 0.47, 95% CI: 0.30-0.75). Antibiotics may also delay the onset of labor in women with premature rupture of membranes, but this is not usually characterized as tocolysis. In addition to drug-specific contraindications, several general factors may contraindicate delaying childbirth with the use of tocolytic medications.