Coefficient Variations of Serum Levels of Phenytoin, Carbamazepine, and Valproic Acid in Compliant Epileptics

Yun, Hae Jung; Kwon, O Y; Park, K J; Kim, N G; Kim, T Y; Jeon, S C; Hong, J G; Kwak, J H; Lee, Y H; Choi, N C; Lim, B H

Abstract

Compliance of epileptic patients is one of the most important factors for adequate therapy. Recently, it had been shown that the variability of three serial measurement of the serum levels of antiepileptic drug(AED) may be used as an indication of the degree of compliance. Coefficient variation(CV) of serum drug levels calculated by only one AED had been used to determine the compliance in epileptic patients who took multiple AEDs. We attempted to evaluate the CV of AEDs and then find the objective clue of compliance and the compatible therapeutic planing according to CV. Ninety seven epileptic patients of outpatients department of the Gyengsang National University Hospital were entered to this study. All patients were taking medication at least for 6 months without any changes of drug regimen. Patient's information was acquired by reviewing the chart and interview with questionnaire. With these informations, we determined the compliance of the patients. Antiepileptic serum levels were measured three times at intervals of at least two to four weeks apart, and their CV was calculated. We compared the CV between the compliant and non-compliant group in each AED(phenytoin, carbamazepine , valproic acid) and three drugs in the compliant group. The mean CVs of phenytoin, carbamazepine and valproic acid in the compliant group were 18.3+/-13.0, 15.2+/-10.2 and 23.8+/-8.9, respectively(mean+/-SD). The mean of CV in the compliant and the non-compliant group were 17.9+/-10.9 and 38.8+/-27.2, respectively. The CVs of the compliant group were significantly lower than those of the non-compliant group(p<0.05). However, CVs had no significant difference between three antiepileptic drugs. This study showed that CVs of AEDs were not different between each AEDs, even though they possess different pharmacokinetic properties. Therefore, the CV of one AED can be used in determining the compliance of the epileptics who are taking multiple AEDs.