Factors associated with blood carnitine levels in adult epilepsy patients with chronic valproic acid therapy.

AIMS: Valproic acid (VPA) is a widely used antiepileptic drug for the treatment of epilepsy, seizures, and bipolar and psychiatric disorders. A deficiency of carnitine, a compound involved in energy production, is associated with chronic VPA use. However, the clinical factors affecting blood carnitine levels and their pathophysiology remain unclear. Hence, we aimed to identify the factors that correlated with serum carnitine levels in epilepsy patients receiving chronic VPA therapy.

METHODS

This observational study included 138 epilepsy patients receiving chronic VPA therapy. Serum total and free carnitine levels, routine blood tests and drug concentrations were assessed. The correlation between carnitine levels and other factors were calculated using Spearman's rank correlation coefficients, and a principal component analysis (PCA) and a multiple linear regression analysis were performed.

RESULTS

Overall, serum free carnitine levels showed significant negative correlations with epilepsy duration, VPA treatment duration, daily VPA dose, and blood VPA concentration. A significant positive correlation was observed with erythrocyte count, hemoglobin levels, and creatinine levels. Of the 138 patients, 21 (15.2 %) with serum free carnitine levels of <20 μmol/L had significantly longer disease duration, a higher daily VPA dose, and lower blood clobazam concentrations. In the 48 VPA monotherapy patients, serum free carnitine levels showed a significant negative correlation with disease duration and duration of VPA therapy. Furthermore, in the 2.1 % patients receiving VPA monotherapy, serum free carnitine levels were <20 μmol/L. PCA resulted in seven factor solution (eigenvalue >1; 71.67 % explained variance). Component 1 clearly revealed the maximal loading for serum free carnitine level (.792) and the most negative loading for disease duration of epilepsy (-.595). A linear regression analysis revealed that the duration of epilepsy, serum creatinine level, and daily dose of VPA were significant (p < .01) factors that affected serum free carnitine levels.

CONCLUSIONS

The effects of combination therapy with VPA and other anti-epileptic drug(s) on carnitine levels are higher than that of VPA monotherapy. Additionally, epilepsy duration may affect serum free carnitine level.