[Pharmacokinetics of anticonvulsants in the perinatal period].

We have examined the concentration of a range of anticonvulsant drugs in serum, amniotic fluid and breast milk in 23 pregnant patients. Drug determinations were made during the last 3 months of pregnancy, at birth and during the first week postpartum. In the cord serum the range of concentrations, expressed as a percentage of the maternal serum concentration was: primidone (67-131%), phenobarbitone (80-108%), carbamazepine (60-76%), phenytoin (95-162%), ethosuximide (104%), and valproic acid (125-147%). In the amniotic fluid the corresponding ranges were: primidone (62-230%), phenobarbitone (28-59%), carbamazepine (18-45%), phenytoin (18-60%), ethosuximide (111%) and valproic acid (5-11%). In breast milk the corresponding percentages were: primidone (44-228%), phenobarbitone (20-50%), carbamazepine (32-80%), phenytoin (46-53%), ethosuximide (92%) and valproic acid (2-8%). Anticonvulsant drugs can be given in relatively high doses during pregnancy. Pregnant patients and neonates are patients with therapeutic problems. For this group of patients is recommendable a therapeutic drug monitoring.