Nifedipine After Atosiban for Tocolysis
Nifedipine retard preparation should not be started immediately after Atosiban due to potential synergistic hypotensive effects, as calcium channel blockers should not be given concomitantly with magnesium sulfate, which is often used alongside tocolytic therapy. 1
Safety Concerns with Sequential Tocolytic Use
- Calcium channel blockers like nifedipine should not be given concomitantly with magnesium sulfate due to risk of hypotension from potential synergism 1
- The European Society of Cardiology and European Society of Hypertension specifically warn against this combination in their position paper on peripartum management of hypertension 1
- Different classes of tocolytics should not be combined due to increased risk of adverse effects (Grade C recommendation) 2
Appropriate Tocolytic Management
- Both atosiban and nifedipine are effective tocolytics for delaying delivery for 48-72 hours to allow for administration of antenatal corticosteroids 3, 4
- The primary goal of tocolytic therapy is not to prevent preterm birth entirely but to gain time for interventions that improve neonatal outcomes 3
- Tocolytic therapy should be prescribed for up to 48 hours only (Grade B recommendation) 2
Comparative Efficacy of Atosiban vs. Nifedipine
- Atosiban has fewer failures within 48 hours compared to nifedipine (68.6% vs 52% success rate, p=0.03) 5
- However, nifedipine may be associated with longer postponement of delivery (mean gestational age at delivery 36.4 weeks with nifedipine vs. 35.2 weeks with atosiban, p=0.01) 5
- NICU admission occurred less often after nifedipine (46%) than after atosiban (59%) (OR 0.32,95% CI 0.14-0.75) 6
Management Recommendations
- If initial tocolysis with atosiban fails, another treatment with a different class of tocolytic (such as nifedipine) may be proposed, but only after the effects of the first agent have worn off 2
- Maintenance tocolysis after the initial 48-hour treatment is not recommended and is potentially harmful (Grade C recommendation) 2
- When switching between tocolytic agents, allow sufficient time for clearance of the first agent to avoid potential drug interactions 1
Special Considerations
- Nifedipine is orally administered and less expensive compared to atosiban (intravenous administration) 2
- Maternal side effects are generally higher with nifedipine compared to atosiban 7
- There is a non-significant trend toward higher neonatal mortality with nifedipine compared to atosiban that warrants careful consideration (OR 1.4,95% CI 0.60-3.4) 6
Clinical Application
- For women with threatened preterm labor between 24-34 weeks gestation, either atosiban or nifedipine can be used as first-line tocolytic agents 3, 4
- If switching from atosiban to nifedipine is clinically necessary, ensure complete clearance of atosiban and any concomitant medications like magnesium sulfate before initiating nifedipine 1
- Monitor maternal blood pressure closely if transitioning between tocolytic agents due to potential cardiovascular effects 1