Nifedipine Dosage for Preterm Labor
The recommended dosage of nifedipine for preterm labor is 10-20 mg orally initially, which can be repeated after 30 minutes if needed, followed by maintenance therapy of 20 mg every 4-6 hours for up to 72 hours. 1, 2
Initial Dosing
- For immediate tocolysis, use immediate-release nifedipine 10-20 mg orally, which can be repeated in 30 minutes if contractions persist 1, 2
- Maximum initial dosing should not exceed 40 mg within the first hour 2
- Onset of action occurs within 5-10 minutes after oral administration 1
Maintenance Dosing
- After initial tocolysis is achieved, switch to maintenance dosing of 20 mg every 4-6 hours for up to 72 hours 2, 3
- Some regimens use slow-release formulations for maintenance at doses of 60-80 mg daily 4
- The goal of tocolysis is to delay delivery for at least 48 hours to allow for administration of antenatal corticosteroids 1
Monitoring and Precautions
- Close monitoring of maternal blood pressure is essential, as nifedipine can cause hypotension 1, 5
- Target blood pressure should be maintained above 90/60 mmHg to prevent maternal hypotension 2
- Avoid concurrent administration with magnesium sulfate due to risk of severe hypotension from potential synergistic effects 1, 5
- Short-acting nifedipine should be used only for acute tocolysis, not for long-term maintenance therapy 6
Efficacy and Alternatives
- Nifedipine has been shown to be more effective than indomethacin in quickly treating preterm labor (75% vs 41% response rate) 7
- Compared to terbutaline, nifedipine has similar efficacy with fewer maternal side effects 2
- If nifedipine is unavailable or contraindicated, alternative tocolytics include labetalol (200 mg orally) or methyldopa (1.0-1.5 g orally) 1
Special Considerations
- In women with skeletal dysplasia, dosing may need to be adjusted according to body size and volume of distribution 1
- For women with hypertension and preterm labor, nifedipine can effectively treat both conditions simultaneously 8
- Higher-dose regimens may reduce the need for rescue treatment compared to lower-dose regimens 4
Duration of Treatment
- Tocolytic treatment should generally be limited to 48-72 hours, which is sufficient time for corticosteroid administration to improve fetal lung maturity 1
- Extended maintenance therapy beyond 72 hours has not been shown to significantly prolong pregnancy compared to no treatment after initial tocolysis 3