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Isoxsuprime dosage for acute and maintenance tocolysis

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isoxsuprine tocolysis preterm labor

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Isoxsuprine Dosage for Tocolysis

Isoxsuprine is a beta-sympathomimetic (beta-adrenergic agonist) used as a tocolytic agent to inhibit uterine contractions in preterm labor. It acts on uterine beta-2 receptors to relax the myometrium.
Important note: Isoxsuprine (along with ritodrine) has been discontinued in the United States. It remains in use in several other countries, particularly in South Asia and parts of Africa.

Acute (IV) Tocolysis

RouteDose
IV infusion0.2-0.5 mg/min
The IV route is used for acute suppression of preterm labor contractions. The infusion is typically started at the lower end (0.2 mg/min) and titrated upward based on response and maternal tolerance. Contractions are usually suppressed within 30-60 minutes. The infusion is maintained for a period after contractions cease, then stepped down.

Maintenance Tocolysis

RouteDose
Oral (PO)20 mg every 6 hours
After IV tocolysis achieves uterine quiescence, oral maintenance therapy is initiated. The standard regimen is 20 mg PO q6h (i.e., 80 mg/day).
Some protocols also use:
  • 10-20 mg PO every 4-6 hours (varying by institutional protocol)

Monitoring and Side Effects

Being a beta-sympathomimetic, isoxsuprine carries a significant maternal side-effect profile:
  • Cardiovascular: tachycardia, palpitations, hypotension (peripheral vasodilation)
  • Metabolic: hyperglycemia, hypokalemia
  • Pulmonary: risk of pulmonary edema (especially with concurrent corticosteroid use or fluid overload)
  • Fetal/neonatal: fetal tachycardia, neonatal hypoglycemia, hypotension, ileus
Continuous maternal cardiac monitoring is required during IV infusion.

Contraindications to Tocolytics (General)

  • Fetal compromise or major congenital anomalies
  • Intrauterine infection (chorioamnionitis)
  • Placental abruption
  • Eclampsia
  • Significant cervical dilation (advanced labor)
  • Preterm premature rupture of membranes (PPROM) in certain settings
Source: ROSEN's Emergency Medicine: Concepts and Clinical Practice - Box 176.3 "Commonly Used Tocolytic Agents"
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