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Valproic acid binding to human serum and human placenta in vitro
David N Bailey1, John R Briggs
1Division of Laboratory Medicine, Department of Pathology, University of California, San Diego, San Diego, California 92103-8320, USA. dnbailey@ucsd.edu
Therapeutic Drug Monitoring
|May 21, 2005
Summary
Valproic acid, an antiepileptic drug, does not bind significantly to the placenta. Transplacental transfer likely occurs via passive diffusion, not placental binding.
Area of Science:
- Pharmacology
- Biochemistry
- Obstetrics
Background:
- Valproic acid is an antiepileptic drug with teratogenic potential.
- Understanding its transplacental transfer is crucial for managing epilepsy during pregnancy.
- The role of placental binding in drug transfer is not fully elucidated.
Purpose of the Study:
- To investigate the binding characteristics of valproic acid in human serum and placenta.
- To define the mechanisms of transplacental transfer of valproic acid.
- To determine if the placenta acts as a depot for valproic acid.
Main Methods:
- Equilibrium dialysis was used to study drug binding.
- Valproic acid binding was assessed in human serum.
- Valproic acid binding was assessed in homogenates of whole human placenta.
Main Results:
- Two binding sites for valproic acid were identified in human serum: one low-capacity, high-affinity and one high-capacity, low-affinity.
- Minimal, nonspecific binding of valproic acid to the placenta was observed.
- Placental binding does not appear to mediate the transplacental transfer of valproic acid.
Conclusions:
- Transplacental transfer of valproic acid is likely mediated by passive diffusion.
- Lipophilicity and pH gradients across the placenta may facilitate valproic acid transfer.
- The placenta does not function as a depot for valproic acid.