Calcium antagonists are preferred above all other
tocolytic agents in the Royal College guidelines because
of their effectiveness and tolerability (5), and
they are being used increasingly often in Germany as
well. They inhibit both the direct influx of calcium
into myocytes and the release of intracellular calcium
(Figure 4). A Cochrane meta-analysis of twelve
randomized and controlled trials revealed that nifedipine,
the most commonly used calcium antagonist, is
superior to betamimetics with respect to the prolongation
of pregnancy by seven days and past the 34th
week of gestation (22). The administration of nifedipine
lowers the frequency of neonatal intraventricular
hemorrhage (OR 0.53, 95% CI 0.34–0.84), respi -
ratory distress syndrome (OR 0.63, 95% CI
0.46–0.86), and necrotizing enterocolitis (OR 0.21,
95% CI 0.05–0.94) (23). Its side effects, including
nausea, flushing, headache, palpitations, and (often)
reflex tachycardia, are less severe than those of betamimetics
(18).