Duodaline (Ritodrine) for Uterine Relaxation
Critical Clarification
Duodaline (ritodrine) is NOT indicated for acute uterine relaxation in obstetric emergencies such as retained placenta or uterine inversion. Ritodrine is a beta-2 adrenergic agonist specifically approved only for the inhibition of preterm labor, not for acute uterine relaxation during delivery complications 1, 2.
Appropriate Use: Preterm Labor Only
Intravenous Administration for Active Preterm Labor
- Initial IV infusion: Start at 50-100 mcg/min, gradually increasing by 50 mcg/min every 10 minutes until uterine contractions cease or maternal heart rate exceeds 140 bpm 2
- Typical effective dose range: 150-350 mcg/min 2
- Duration: Continue IV infusion for 12-24 hours after contractions stop, then transition to oral maintenance 3, 2
- Treatment initiation time: Ritodrine typically begins inhibiting uterine activity within 2.33 ± 0.63 hours 3
Oral Maintenance Therapy
- Dosing: Two 40 mg sustained-release capsules three times daily 4, 5
- Duration: 7 days of maintenance therapy after successful IV tocolysis 4
- Efficacy controversy: While one study showed reduced recurrence of preterm labor requiring retreatment (1/50 vs 11/45 with placebo) 4, a more recent trial found no benefit over no treatment (8/62 vs 6/58) 5
For Acute Uterine Relaxation: Use Nitroglycerin Instead
When acute uterine relaxation is needed (retained placenta, uterine inversion), nitroglycerin is the recommended pharmacologic agent, NOT ritodrine 6, 7, 8:
- IV nitroglycerin: 50-100 mcg boluses, repeated as needed 7, 8
- Sublingual nitroglycerin: Metered-dose spray as alternative 6, 8
- Alternatives: Terbutaline sulfate or general anesthesia with halogenated agents 6
Safety Profile and Contraindications
Maternal Side Effects
- Cardiovascular: Tachycardia (most common), palpitations, hypotension 2
- Metabolic: Hyperglycemia, hypokalemia 2
- Pulmonary: Risk of pulmonary edema, especially with concurrent corticosteroids or fluid overload 2
- Other: Tremor, nervousness, nausea 5
Monitoring Requirements
- Continuous maternal heart rate and blood pressure monitoring during IV infusion 2
- Maintain maternal heart rate below 140 bpm 2
- Monitor for signs of pulmonary edema 2
Clinical Pitfalls to Avoid
- Do not use ritodrine for acute uterine relaxation emergencies - it is too slow-acting and not indicated for this purpose 1, 2
- Do not continue IV infusion if maternal tachycardia exceeds 140 bpm - risk of cardiovascular complications 2
- Oral maintenance therapy has questionable benefit - the most recent evidence shows no advantage over no treatment 5
- Limited impact on neonatal outcomes - despite widespread use, ritodrine has had minimal impact on low birth weight incidence nationally 1