Teratology comments
(Aust Prescr 1994;17:12)
Antiepileptics- clinical applications
The incidence of birth defectsin epileptic women taking anticonvulsants is 2-3 times that of the generalpopulation. The highest rate is with multiple drug therapy, then phenytoin,followed by sodium valproate, carbamazepine and phenobarbitone.
There is an increased risk of spina bifida(1-2%) with sodium valproate and carbamazepine, particularly in combinationwith phenytoin. To reduce the risk, folic acid 0.5-4.0 mg daily isrecommended, beginning before conception and continuing until the endof the first trimester. A dysmorphic, Binder-like syndrome (mid-facehypoplasia) may also occur, particularly with phenytoin. It may beassociated with developmental problems.
Anticonvulsant levels should be monitoredfrequently with dose adjustments based on clinical condition, seizurefrequency and free anticonvulsant concentration. Total concentrationlevels may give a false impression and lead to a tendency to increasedosage (see 'Drug protein binding' Aust Prescr 1992;15:56-7). Postpartumanticonvulsant concentrations should be monitored closely to preventtoxicity in either the mother or infant.
To avoid neonatal haemorrhage which isassociated with maternal antiepileptic therapy, particularly phenytoin,the mother is given vitamin K by injection from 2-48 hours before delivery,and the infant should receive a vitamin K injection at birth.
Breast-feeding may be undertaken, withclose monitoring of the infant for any signs of prolonged drowsinessor feeding problems (most likely with clonazeparn or phenobarbitone).
