Effect of Dosage Form and Combined Drug on Plasma Concentrations of Antiepileptics

The concentrations of diphenylhydantoin (DPH) and phenobarbital (PB) in the plasma obtained from the outpatients with epilepsy were determined by the enzyme multiplied immunoassay technique (EMIT), and the results were recorded on a data sheet which was named “Monitoring Chart” of the respective patients.These data were retained and possible correlations were analyzed, and the plasma concentrations of DPH were found to be higher when DPH was administered in the dosage form of tablet than when administered in the form of powder. It was also suggested that the concentrations of DPH were decreased when the other antiepileptics such as PB and valproic acid (VPA) were used in combination. However, PB in the blood was increased when it was combined with VPA or DPH.