Serum alkaline phosphatase isoenzymes in epileptic children receving anticonvulsant drugs.

In 40 epileptic children on long-term anticonvulsant treatment, serum alkaline phosphatase (AP) isoenzymes were separated semiquantitatively using a combination of L-phenylalanine inhibition and heat inactivation. Though mean total serum AP activity was significantly increased compared to age matched controls, only 4 individual values exceeded the upper limit (mean + 2SD) of the reference sample. In epileptics the mean activity of the heat-sensitive non L-phenylalanine sensitive AP fraction (non-LPSAP) was significantly increased (P less than 0.01) and the mean Q-value (i.e. percentage ratio of heat-stable non-LPSAP/non-LPSAP) was significantly decreased (P less than 0.05), thus indicating an enhancement of the bone isoenzymes during anticonvulsant treatment. In 4 patients the isoenzyme pattern was abnormal although total serum AP activity was normal and in 3 of them the deviation indicated enhanced bone isoenzyme. The data provide evidence that in anticonvulsant treated children the bone isoenzyme, rather than hepatobiliary isoenzyme fraction, may be increased even when total serum AP activity is normal. Thus, semiquantitative separation of serum AP isoenzymes may be a helpful guide as to whether or not an eplieptic child should be given vitamin D.