Nifedipine Protocol for Tocolysis
For acute tocolysis in preterm labor, administer nifedipine 10 mg orally every 15-20 minutes for up to 40 mg in the first hour, followed by 20 mg slow-release formulation every 8 hours for maintenance therapy. 1, 2
Initial Loading Dose Protocol
- Administer 10 mg immediate-release nifedipine capsules orally every 15-20 minutes, up to a maximum of 40 mg in the first hour 1, 3
- Oral administration is preferred over sublingual, though sublingual may achieve faster tocolysis (160 minutes vs 340 minutes to achieve uterine quiescence) 2
- Peak plasma concentration occurs at approximately 1.2 hours, reaching 127.2 ± 44 ng/mL, which is effective for achieving tocolysis 1
Maintenance Therapy
- After the loading dose, transition to 20 mg slow-release nifedipine at 90 minutes, then continue 20 mg every 8 hours (total 60 mg/day) 1, 4
- Alternative regimen: Nifedipine GITS (gastrointestinal therapeutic system) 90 mg/day may be used with similar efficacy and potentially better tolerance (fewer headaches) 4
- Maintenance tocolysis beyond 48 hours after initial tocolysis and corticosteroid completion does not significantly reduce adverse perinatal outcomes and is not recommended 5
Therapeutic Plasma Levels
- Mean plasma concentration for effective tocolysis is approximately 67.4 ± 28.4 ng/mL during the first 4 hours 1
- In steady state, the required plasma concentration is approximately half of that needed during initial tocolysis 1
Safety Monitoring
- Monitor for common side effects including flushing, headache, and hypotension (particularly in hypovolemic patients) 3
- Nifedipine demonstrates minimal adverse hemodynamic effects when used for tocolysis 1
- Do not combine with magnesium sulfate due to risk of precipitous blood pressure drop 6
Clinical Indications and Contraindications
- Indicated for preterm labor between 24-36 weeks gestation with cervical dilatation ≤4 cm, effacement ≤80%, and intact membranes 2
- Nifedipine is as effective as beta-mimetics for tocolysis with fewer discontinuations due to side effects 3
- Avoid immediate-release nifedipine in patients with cardiovascular disease without concomitant beta-blockade 6, 7
Important Caveats
The evidence shows that while nifedipine effectively achieves acute tocolysis, prolonged maintenance therapy beyond the initial 48-hour window (after corticosteroid completion) does not improve perinatal outcomes 5. Therefore, limit tocolysis to the time needed for corticosteroid administration and maternal transport if necessary, rather than extended maintenance protocols.