Drugs & Medication

Tocolytics are medications used to suppress premature labor (toco refers to contractions, and lytic to removal). They are nearly always given in midpregnancy during preterm labor, when delivery would result in an extremely premature infant. This therapy is mainly instituted so that administration of glucocorticoids (which accelerate fetal lung maturity) can begin.

During administration of tocolytic medications, the mother's condition and the fetal heart rate pattern will be closely monitored by a health care professional to determine effects the medication is having on the mother and fetus' well being. If medication as well as other interventions fail to have the desired effect, immediate cesarian delivery may be required. Tocolytic therapy can delay birth by up to several days at its best.

Types of agents

Various types of agents are used, with varying success rates and side effects. Some medications are not FDA approved specifically for use in stopping uterine contractions in preterm labor, but are still used off label. Magnesium sulfate is the most commonly used tocolytic agent.

Examples:

• MgSO₄
• Ritodrine (Yutopar)
  Fenoterol
  Nifedipine (Procardia, Adalat)
  Atosiban
  Indomethacin
  Terbutaline (Brethine)

Ethyl alcohol was frequently prescribed as a tocolytic in the mid-20th century, but later double-blind studies^[1] have not shown it to be effective.

Contraindications to Tocolysis

Several factors may contraindicate delaying birth with the use of tocolytic medications. ^[2]

• Fetus is older than 37 weeks gestation
  Fetus weighs more than 2500g or has IUGR
  Fetus is in acute distress or has passed (or has a fatal anomaly)
  Dilation is greater than 4 cm
  Chorioamnionitis or intrauterine infection is present
  Mother has severe PIH, eclampsia, active vaginal bleeding, a cardiac disease, or another condition which indicates that the pregnancy should not continue.

References

1. ↑  Castren O, Gummerus M, Saarikoski S. Treatment of imminent premature labour. Acta Obstet Gynecol Scand 1975;54:95–100. [3]

1. ↑ Wong, Perry, and Hockenberry. Maternal Child Nursing Care. Mosby 2002