What is the role of terbutaline in tocolysis?

Role of Terbutaline in Tocolysis

Terbutaline should not be used for tocolysis due to serious maternal and fetal risks, including death, cardiac arrhythmias, pulmonary edema, and myocardial ischemia. 1 The FDA has explicitly warned against using oral terbutaline for acute or maintenance tocolysis, particularly in outpatient or home settings.

Safety Profile and FDA Warning

Terbutaline carries a boxed warning from the FDA specifically addressing its use in tocolysis:

• Not approved for acute or maintenance tocolysis
• Associated with serious adverse reactions including death in pregnant women
• Maternal risks include increased heart rate, transient hyperglycemia, hypokalemia, cardiac arrhythmias, pulmonary edema, and myocardial ischemia
• Fetal/neonatal risks include increased heart rate and neonatal hypoglycemia 1

Alternative Tocolytics

Current guidelines recommend other agents for tocolysis when clinically indicated:

1. First-line options:

   • Nifedipine (calcium channel blocker)
   • Indomethacin (NSAID)
   • Magnesium sulfate 2

2. Goal of tocolysis:

   • Primarily to delay delivery for 48 hours to allow for corticosteroid administration to improve neonatal outcomes
   • Not intended for long-term prevention of preterm birth 2

Historical Context and Research Evidence

Despite the FDA warning, terbutaline has historically been used for tocolysis:

• Some research suggested terbutaline may be effective in prolonging pregnancy beyond 48 hours compared to salbutamol 3
• A 1998 review argued for continued use of terbutaline as one of few options for preventing preterm birth 4
• A comparative study found terbutaline and nifedipine had similar tocolytic effects, but terbutaline was associated with more adverse effects overall 5

Acute Tocolysis for Fetal Distress

In acute situations involving fetal distress requiring immediate intervention:

• Terbutaline (0.25 mg subcutaneously) has been shown to reduce uterine activity more rapidly (1.8 ± 0.74 minutes) compared to magnesium sulfate (7.5 ± 2.1 minutes) 6
• However, this specific use case differs from maintenance tocolysis for preterm labor

Other Medical Uses of Terbutaline

While contraindicated for tocolysis, terbutaline has legitimate uses in other medical contexts:

• Asthma management: Classified as a short-acting β2-agonist (SABA) that can be used during pregnancy for asthma management 2
• External cephalic version: Has shown efficacy as a tocolytic agent for external cephalic version procedures 7
• Prolonged erections: May be effective in treating prolonged erections (less than 4 hours) following pharmacologic stimulation 2

Common Side Effects

When used for any indication, terbutaline commonly causes:

• Tremor (76.4%)
• Nausea (58.8%)
• Dizziness (29.4%)
• Maternal and fetal tachycardia
• Maternal hyperglycemia
• Neonatal hypoglycemia 5, 2

Clinical Decision Making

Given the FDA warning and availability of safer alternatives, clinicians should:

1. Never use terbutaline for:

   • Maintenance tocolysis
   • Outpatient tocolysis
   • Home-based tocolysis

2. Consider safer alternatives first:

   • Nifedipine
   • Indomethacin
   • Magnesium sulfate

3. Document thoroughly if using for non-tocolytic purposes:

   • Asthma management
   • External cephalic version
   • Other approved indications

Conclusion

Despite some historical use and research suggesting efficacy, the serious risks associated with terbutaline for tocolysis outweigh potential benefits. The FDA warning should be heeded, and safer alternatives should be used when tocolysis is indicated.