What is the maximum dose of nifedipine (calcium channel blocker) for preterm labor?

Maximum Dose of Nifedipine for Preterm Labor

The maximum daily dose of nifedipine for preterm labor is 120 mg daily or 60 mg twice daily. 1

Dosing Regimen for Preterm Labor

• Initial loading dose options:

  • 10 mg oral nifedipine (immediate-release) every 15-20 minutes, up to 40 mg in the first hour 2, 3
  • 20 mg loading dose, which may be repeated in 30 minutes for high-dose regimens 4

• Maintenance therapy options:

  • Standard dose: 60-80 mg slow-release nifedipine daily for 48 hours, followed by 60 mg daily until 36 weeks 4
  • Higher dose: 120-160 mg slow-release nifedipine daily for 48 hours, followed by 80-120 mg daily until 36 weeks 4

Administration Considerations

• Nifedipine should be administered orally, not sublingually, as sublingual administration increases the risk of sudden hypotension 5, 6
• Maternal blood pressure should be monitored closely, especially during the first hour of treatment 5, 6
• The goal of tocolysis is to delay delivery for at least 48 hours to allow time for corticosteroid administration for fetal lung maturity 6

Efficacy and Safety Considerations

• Higher-dose nifedipine regimens (120-160 mg daily) may result in higher gestational age at delivery compared to lower-dose regimens (60-80 mg daily) 4
• Patients on lower-dose regimens may require rescue treatment more frequently than those on higher-dose regimens 4
• Plasma concentrations of approximately 67 ng/mL have been shown to achieve effective tocolysis 3

Precautions and Contraindications

• Nifedipine should be used with caution when combined with magnesium sulfate due to the risk of precipitous blood pressure drop 5, 6
• Nifedipine is contraindicated in heart failure 1
• Common side effects include flushing, headache, and peripheral edema 1, 5
• Nifedipine is not FDA-approved specifically for preterm labor management but is used off-label for this indication 5, 6

Monitoring

• Blood pressure should be monitored regularly, particularly during initial administration 5, 6
• Assess for common side effects including dizziness, headache, and flushing 5
• Monitor for signs of hypotension, especially if combined with magnesium sulfate 6

Clinical Considerations

• Nifedipine has been shown to be as effective as beta-mimetics (such as terbutaline) for tocolysis but with fewer side effects requiring discontinuation 2, 7
• The titration interval for nifedipine in stable patients is typically 5-7 days 1
• Maintenance therapy with oral nifedipine after initial tocolysis with magnesium sulfate has not been shown to significantly prolong pregnancy compared to no maintenance therapy 8