Precursor prothrombin status in patients receiving anticonvulsant drugs.

Protein induced by vitamin K absence (PIVKA) is the circulating prothrombin precursor found in considerable concentrations when carboxylation of prothrombin is impaired. In this study PIVKA-positivity was assessed in adult epileptic patients receiving a variety of anticonvulsant drugs. Mean PIVKA (+/- SD) concentration was 4.6 +/- 2.3% in 16 epileptics vs 1.1 +/- 0.7% in 10 age-matched controls (p less than 0.001). 13 of the 16 (81%) epileptics had PIVKA values above the highest value recorded for the controls (Fisher exact test, p less than 0.001). Other indices of coagulation were normal. There was no correlation between PIVKA concentration and the particular anticonvulsant taken. This study therefore shows that most epileptics on anticonvulsant therapy have a subclinical coagulation defect. These data, together with previous findings of raised PIVKA concentrations in maternal-infant pairs exposed to gestational anticonvulsants and reports of neonatal haemorrhage in infants of epileptics, strengthen the case for antenatal vitamin K supplementation in pregnancies complicated by anticonvulsant therapy.