Nifedipine (Adalat OROS) as a Tocolytic Agent
Nifedipine, including extended-release formulations like Adalat OROS, is recommended as a first-line tocolytic agent for preterm labor to delay delivery for 48-72 hours, allowing time for antenatal corticosteroid administration and maternal transfer to tertiary care facilities. 1, 2
Primary Recommendation
Extended-release nifedipine (such as Adalat OROS) is specifically recommended as a first-line maintenance tocolytic agent during pregnancy due to ease of once-daily administration, which improves patient adherence. 3
The American College of Obstetricians and Gynecologists endorses nifedipine alongside indomethacin as preferred tocolytic agents for women with preterm labor and intact membranes after 26 weeks of gestation. 1, 2
The long-acting formulation should be used as maintenance medication during pregnancy, while short-acting formulations are reserved only for rapid treatment of severe hypertension. 3
Clinical Algorithm for Use
When to initiate:
- Gestational age between 24-34 weeks with confirmed preterm labor (regular uterine contractions with cervical change). 1
- Intact membranes without contraindications to tocolysis. 1
Concurrent interventions:
- Administer antenatal corticosteroids (24-34 weeks). 1
- Consider magnesium sulfate for fetal neuroprotection if less than 32 weeks' gestation. 1
- Do NOT use antibiotics for preterm labor with intact membranes (no evidence of benefit and potential harm). 1
Critical Safety Considerations
Absolute contraindications and warnings:
Never combine nifedipine with magnesium sulfate, as this combination can induce uncontrolled hypotension and fetal compromise. 3, 1
Exercise extreme caution when maternal cardiovascular status is compromised, including intrauterine infection, twin pregnancy, maternal hypertension, or cardiac disease—life-threatening pulmonary edema and cardiac failure are definite risks. 4
Short-acting nifedipine should be avoided except in low-resource settings when other drugs are unavailable, as it has been shown to induce uncontrolled hypotension, particularly when combined with magnesium sulfate, resulting in fetal compromise. 3
Common Side Effects
- Patients may experience headaches, tachycardia, or edema as side effects. 3
- If these occur, labetalol can be used as an alternative or in combination with nifedipine for uncontrolled blood pressure. 3
Evidence Quality and Limitations
The primary benefit of tocolytics is gaining time for corticosteroid administration and maternal transfer, not preventing preterm birth itself. 2
Despite ability to delay delivery temporarily, no tocolytic (including nifedipine) has been consistently shown to improve neonatal outcomes or reduce the overall rate of preterm birth. 5, 2
The goal is specifically to delay delivery for 48-72 hours to allow maximal effect of antenatal corticosteroids. 1, 5
Dosing Considerations
Initial tocolysis can be achieved with 10 mg nifedipine capsules orally every 15 minutes up to 40 mg in the first hour, followed by 20 mg slow-release formulation at 90 minutes. 6
This regimen achieves effective plasma concentrations (mean 67.4 ng/mL) for tocolysis without adverse hemodynamic side effects. 6
Comparative Effectiveness
Nifedipine appears more effective than betamimetic agents in prolonging pregnancy for 7 days or longer, is much less likely to cause maternal side effects, and is associated with reduced neonatal morbidity. 7
Meta-analyses comparing nifedipine with intravenous labetalol for severe hypertension found nifedipine as efficacious and safe, though evidence is based on relatively small sample sizes. 3