Nifedipine

Appears to produce fewer side effects, but studies are lacking

Updated 3/5/01

Nifedipine, also known as Procardia, is in a class of drugs known as calcium channel blockers. Nifedipine's original use is as a heart drug. It also is a smooth muscle relaxer that inhibits "uterine activity by decreasing calcium influx through voltage-dependent calcium channels." (Clinical Obstetrics and Gynecology, 1995, Vol. 38, p. 736) Nifedipine is typically administered in pill or capsule form.

Nifedipine tablets, when compared to IV Ritodrine, appeared to work better with fewer maternal side effects in a 1997 study (Obstet Gynecology 1997, 90:230-234). More women in the ritodrine group delivered within 24 hours, 1 week and 2 weeks than in the nifedipine group. A 2000 study comparing the two drugs found nifedipine was associated with a lower rate of fetal and newborn deaths than Ritodrine (Obstet Gynecology 2000, 95:477-481).

However, a 1999 study found that nifedipine worked no better than a placebo in preventing a recurrence of preterm labor after labor was stopped with magnesium sulfate (American Journal of Obstetrics and Gynecology 1999, 181:822-827). This finding, if confirmed by other studies, would make nifedipine similar to terbutaline and Ritodrine. Neither of those two drugs were shown to work any better than a placebo after a period of 24-48 hours. In other words, long-term maintenance therapy with these preterm labor drugs didn't work any better than no treatment at all.

Maternal side effects are less severe than with beta-adrenergics such as terbutaline. Nifedipine's maternal side effects include:

Tachycardia
Cutaneous flushing
Headache
Dizziness
Nausea
Vasodilation
(Rarely) Hypotension
(Reports) Drug-induced maternal hepatotoxicity

Animal studies have showed some fetal side effects that were not replicated in human studies. However, "sparse data are available" on the side effects of this drug. (Clinical Obstetrics and Gynecology, 1995, Vol. 38, p. 736)

CAUTION: Nifedipine, when combined with magnesium sulfate, can cause neuromuscular blockade and severe muscle weakness. (Clinical Obstetrics and Gynecology, 1995, Vol. 38, p. 736)

Journal of the American Medical Association review

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