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Phenoxybenzamine placental transfer during the third trimester
M L Santeiro1, C Stromquist, L Wyble
1Department of Pharmaceutical Care, Tampa General Hospital, FL 33601, USA.
The Annals of Pharmacotherapy
|November 1, 1996
Summary
Phenoxybenzamine crosses the placenta during maternal pheochromocytoma treatment, leading to fetal accumulation. Newborns may experience perinatal depression and hypotension, requiring close monitoring.
Area of Science:
- Obstetrics and Gynecology
- Pharmacology
- Neonatology
Background:
- Maternal hypertension secondary to pheochromocytoma requires careful management during pregnancy.
- Phenoxybenzamine is an alpha-adrenergic blocker used to control blood pressure in such cases.
Observation:
- A 22-year-old pregnant patient with pheochromocytoma received phenoxybenzamine and labetalol.
- Placental transfer was assessed by measuring phenoxybenzamine concentrations in maternal plasma, cord blood, and amniotic fluid at delivery.
- Newborn blood samples were collected at 32 and 80 hours of life.
Findings:
- Phenoxybenzamine demonstrated placental transfer, with cord plasma concentrations higher than maternal plasma (fetal-maternal ratio 1.6:1).
- Mean phenoxybenzamine concentrations were 103.3 ng/mL in cord plasma, 66 ng/mL in maternal plasma, and 79.3 ng/mL in amniotic fluid.
- The newborn exhibited perinatal depression and transient hypotension in the first few days of life, with plasma concentrations of 22.3 ng/mL at 32 hours.
Implications:
- Phenoxybenzamine therapy during pregnancy can lead to fetal exposure and accumulation.
- Neonates exposed to phenoxybenzamine may present with respiratory depression and hypotension.
- Close neonatal monitoring is crucial for early detection and management of adverse effects.