Preterm birth occurs in around 12 percent of pregnancies in the United States, according to the March of Dimes. Treatments to stop true preterm labor with cervical dilation have limited success, according to obstetrician Robert Barbieri, M.D. Magnesium sulfate has been given either by injection or intravenous infusion to treat preterm labor in the United States. Magnesium gluconate, an oral medication, may be given as a follow-up prophylaxis for preterm delivery to patients discharged from the hospital after magnesium sulfate therapy.
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Magnesium can relax smooth muscle. Since the uterus consists of smooth muscle, magnesium may cause relaxation that stops uterine contractions. Magnesium competes with calcium and interferes with calcium-activated enzyme reactions that lead to muscle contraction.
Positive Studies
Researchers from the University of Mississippi Medical Center compared the effectiveness of magnesium gluconate to ritodrine once labor was halted with intravenous magnesium sulfate. The study, published in the June 1988 issue of the "American Journal of Obstetrics and Gynecology," found the drugs similar in efficacy, with pregnancy being prolonged approximately six weeks before delivery.
Negtive Studies
A study of the effects of a 1g dose of magnesium gluconate four times daily as prophylaxis in a group of 54 women, half of whom received the drug and half of whom received the placebo, was also conducted by researchers from the University of Mississippi Medical Center. The study, published in the January 1992 issue of the "American Journal of Obstetrics and Gynecology," found that magnesium gluconate was no more successful at preventing preterm delivery than placebo. The mean serum concentration of magnesium in the treated group was only 0.10 mg/dL, an amount considered not significant, according to researchers.
Potential Side Effects
Oral magnesium gluconate is taken in a smaller dose than that received through an infusion in the hospital, which reduces the risks of complications. Serum levels of magnesium that exceed 4 to 5 mEq/L can cause more serious symptoms, according to Drugs.com. Common symptoms of magnesium therapy include diarrhea, nausea, flushing and sweating. At higher serum levels, 4 to 7 mEq/L, loss of deep tendon reflexes, confusion, sedation and muscle weakness can occur. Levels between 7 to 10 mEq/L cause respiratory depression and a drop in blood pressure, since magnesium can cause vasodilation.
References
- March of Dimes; Preterm labor and birth: A serious pregnancy complication; April 2010
- OBG Management; Is the End of an Era Here for Magnesium Sulfate Tocolysis? Robert Barbieri, M.D.; January 2007
- Drugs.com: Magnesium Gluconate
- "American Journal of Obstetrics and Gynecology"; Comparison of Ritodrine and Magnesium Gluconate for Ambulatory Tocolysis; R. Martin, et al.; June 1988
- "American Journal of Obstretrics and Gynecology"; Oral Magnesium and the Prevention of Preterm Labor in a High-Risk Group of Patients; R. Martin, Et al.; January 1992
