Single Dose of Pindolol in Normotensive Pregnancy: The Lack of Changes in Hemodynamics in Spite of Effective Beta-Receptor Binding

Abstract

Objective: To evaluate the absorption, placental transfer, receptor occupancy, and acute hemodynamic effects of a single peroral dose of pindolol in healthy term pregnancy.

Methods: Ten pregnant healthy women admitted for cesarean section at term after uneventful pregnancy received each 5 mg of pindolol perorally before operation. The acute hemodynamic responses were measured, and maternal and fetal circulations were assessed with color Doppler ultrasonography. Pindolol concentrations were measured with a sensitive radioreceptor binding assay, and the corresponding beta₂-receptor occupancy was determined.

Results: Mean maternal concentration of pindolol 1 h after ingestion was 9.4 ng/ml, and it rose to 14.6 ng/ml at the time of cesarean section; respective beta₂-receptor occupancies were 91.8% and 98.8%. In the umbilical artery, pindolol concentration was 50% of the maternal concentration. A plasma concentration of 2.5 ng/ml yielded 90% beta₂-receptor occupancy, which reflects the high potency of pindolol.

Conclusion: Despite almost total blockade of beta₂-receptors, no changes in maternal or fetal hemodynamics or Doppler flow velocity waveforms were observed.

Key Words:

• Doppler ultrasound
• Pindolol
• Pregnancy