Epilepsy in pregnancy

- Decreased protein binding occurs during pregnancy resulting in increased free drug concentrations. 

This is offset by increased volume of distribution, nausea & vomiting and decreased compliance
- Urinary excretion of phenytoin and its metabolites occurs partly with glomerular filtration but, more importantly, by tubular secretion
- Phenytoin is hydroxylated in the liver by an enzyme system which is saturable at high plasma levels - increased drug metabolism and excretion in pregnancy
- Increased risk of neural tube defects with anti-epileptics
- Vitamik K recommended from 36 weeks gestation
 - hepatic enzyme-inducing drugs increase the risk of vitamin K deficiency and haemorrhagic disease in the neonate