Study Citations, Summaries

Cotton, D. B., et al., "Comparison of magnesium sulfate, terbutaline and a placebo for the inhibition of preterm labor," Journal of Reproductive Medicine, 1984, 29, pp. 92-97.

This study of 54 women compared the effectiveness of IV terbutaline, magnesium sulfate and a placebo. It found no difference between the three groups in capability of delaying delivery for at least 48 hours. There also were no signficant differences between the groups in gestational age at delivery, birthweight and neonatal survival.

Cox, Susan M., et al., "Randomized investigation of magnesium sulfate for the prevention of preterm birth," American Journal of Obstetrics and Gynecology, 1990, Vol. 163, pp. 767-772.

In this study, 156 women experiencing preterm labor were randomized to receive either magnesium sulfate or no therapy. "Compared with control pregnancies, magnesium sulfate tocolysis had no significant effect on the duration of gestation, birth weight, neonatal morbidity and perinatal mortality."

Hollander, David, et al., "Magnesium sulfate and ritodrine hydrochloride: A randomized comparison," American Journal of Obstetrics and Gynecology, 1987, Vol 156, pp. 631-637.

This study compared the effectiveness of treatment with magnesium sulfate versus IV ritodrine in a total of 79 women. Pregnancies were prolonged by more than 72 hours in 88% of the women receiving magnesium sulfate and in 79% of the women receiving ritodrine. Side effects were "less alarming" in the magnesium sulfate group.

Chau, Ann C., et al., "A Prospective Comparison of Terbutaline and Magnesium for Tocolysis," Obstetrics and Gynecology, 1992, Vol. 80, pp. 847-851.

This study compared the effectiveness of magnesium sulfate, oral magnesium, terbutaline shots and oral terbutaline in a group of 98 women. "Significantly more patients in the magnesium group delivered at 37 weeks or more: 34 of 46 versus 27 of 52. No significant differences were found for delivery by 48 hours or 1 week. The interval between treatment and delivery was greater for magnesium."

Miller, J.M., et al., "A comparison of magnesium sulfate and terbutaline for the arrest of preterm labor," Journal of Reproductive Medicine, 1982, Vol. 27, pp. 348-351.

This study of 29 women found that terbutaline (by IV and then pills) and magnesium sulfate were comparable in effectiveness, with 8 patients in each group delivering at 37 weeks or greater.

Tchilinguirian, Nubar, G., et al., "The Use of Ritodrine and Magnesium Sulfate for the Arrest of Premature Labor," International Journal of Gynaecology and Obstetrics, 1984, Vol 22, pp. 117-123.

This study of 67 women (48 with unruptured and 19 with ruptured membranes) treated with either IV ritodrine or magnesium sulfate found the two treatments to be equally effective. For example, in the group with intact membranes, magnesium sulfate treatment resulted in 21 women prolonging their pregnancies by more than 7 days while ritodrine treatement prolong pregnancies by more than 7 days in 16 women. This difference was not statistically significant.

Beall, Marie H., "A comparison of ritodrine, terbutaline, and magnesium sulfate for the suppression of preterm labor," American Journal of Obstetrics and Gynecology, 1985, Vol. 153, pp. 854-859.

In this study, 131 patients with preterm labor were assigned to take IV terbutaline, IV ritodrine or magnesium sulfate. The terbutaline and ritodrine were administered in a double-blind fashion. When failure occured with terbutaline or ritodrine (both in the same family of drugs), women were switched to magnesium sulfate, and vice versa. There was no statistically significant difference between treatments. Note: The rate of side effects was "unacceptably high" for women taking terbutaline. The University of Southern California School of Medicine and Women's Hospital, where the study was held, stopped using terbutaline for that reason.

Wilkins, Isabelle A., et al., "Efficacy and side effects of magnesium sulfate and ritodrine as tocolytic agents," American Journal of Obstetrics and Gynecology, 1988, Vol. 159, pp. 685-689.

This study of 120 women concluded that ritodrine and magnesium sulfate are equally effective. It consisted of 67 women who took ritodrine by IV, 70 women who took magnesium sulfate, and 13 women who took both drugs by IV. The study noted that 77% of the women receiving both drugs together developed side effects "without a demonstrable benefit over a single agent."