CALCIUM CHANNEL BLOCKERS IN OBSTETRICS: THE MANAGEMENT OF PRETERM LABOR
AND HYPERTENSION IN PREGNANCY.
Papatsonis, D.N.M. ‫٭‬1*, Lok C.A.R.1*, Bos J.2#, van Geijn H.P.1*, Dekker G.A.1**
Departments of Obstetrics and Gynecology1, Pharmacy2, Free University Hospital Amsterdam *,
Canisius-Wilhelmina Ziekenhuis Nijmegen, The Netherlands# , North Western Adelaide Health
Service, The University of Adelaide, South Australia**.
Calcium Channel Blockers (CCB’s) have the ability to inhibit contractility in smooth muscle cells.
CCB’s have an already established role in the treatment of non-pregnant hypertension and angina
pectoris, but due to new insights in their action mechanism the number of indications has expanded.
In obstetrics CCB's have become increasingly popular for the management of preterm labor and
pregnancy -induced hypertensive disorders.
Their popularity in the management of preterm labor is at least partially based on the absence of
tachyphylaxis and the low incidence of side effects in comparison with betamimetics.
Meta-analysis shows that use of nifedipine in comparison with betamimetics is associated with a more
frequent successful prolongation of pregnancy in case of preterm labor, resulting in significantly fewer
admissions of newborns to the neonatal intensive care unit , and is associated with a lower incidence
of respiratory distress syndrome. No adverse fetal side effects in humans have been reported with the
use of nifedipine for obstetric indications.
The use of nifedipine is also associated with a lower incidence of maternal and fetal side effects.
The influence on maternal cardiac output and heart rate is mild in contrast to betamimetics, a class of
drugs known to increase cardiac output and to cause tachycardia. Furthermore nifedipine does not
cause fetal tachycardia. The absence of drug-induced fetal tachycardia prevents problems with the
interpretation of the fetal heart rate patterns, since fetal tachycardia in case of betamimetics use may
also be due to intrauterine infection, fetal hypoxia, and other reasons. Thus nifedipine has a minimal
effect on cardiac output, no effect on carbohydrate metabolism and no interference with the
interpretation of fetal heart rate tracings, favors nifedipine for the treatment of preterm labor.
Nifedipine has also the ease of oral administration. In preeclampsia, nifedipine is effective in lowering
blood pressure and may be a good alternative for treatment with (di)hydralazine, which is often
associated with maternal hypotension. Future studies are needed to compare nifedipine with other
new antihypertensive therapies such as ketanserin and nitric oxide donors.
We can conclude that when tocolytic therapy is indicated for preterm labor nifedipine can be used as
an effective and safe drug. In preeclampsia nifedipine effectively lowers blood pressure and can be a
good alternative for (di) hydralazine.
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De Boelelaan 1117, 1081 HV Amsterdam, The Netherlands. E-mail: Hoog.pap@wxs.nl