Evaluation of the effect of long term valproic acid treatment on plasma levels of carnitine, ammonia and amino acids related to the urea cycle in pediatric epileptic patients

INTRODUCTION: Valproic acid (VPA) is an antiepileptic drug widely used in paediatrics. In spite of being a safe and effective anticonvulsant, VPA has been involved in the onset of changes in the metabolism of ammonia and carnitine, although few prospective studies have been made of this. OBJECTIVES: To evaluate the effect of long-term VPA administration, particularly on the metabolism of carnitine, ammonia and plasma amino-acids and the possible clinical repercussions of this in a group of epileptic patients studied prospectively and retrospectively. MATERIAL AND METHODS: A study was made of 102 epileptic children on long term anticonvulsant treatment mainly with VPA. These patients were divided into two groups: group I (n = 25) were studied prospectively (basal sample, after one, six and twelve months of treatment) and group II (n = 77) or long term treatment group (a single sample extraction). In each epileptic patient and in 56 children from a control group (group III) studies were made of free plasma carnitine, ammonia and amino-acids related to the urea cycle and the plasma levels of each anticonvulsant drug. RESULTS: It was observed that in group I there was a fall in plasma carnitine concentrations with time and a progressive rise which was statistically significant (p = 0.001) in plasma levels, mainly of ammonia, glutamine, glycine and ornithine, from the basal levels to those after a year of treatment in practically 100% of the children studied. In group II children on antiepileptic drugs, mainly VPA, were seen to have lower plasma carnitine levels than those in the control group and higher serum ammonia, glutamine and glycine levels than the healthy population not treated with anticonvulsants. These differences were statistically significant (p = 0.001). No relationship was found between the parameters studied and the plasma levels of the drug, type of epilepsy or presence of side effects. CONCLUSIONS: These changes show the negative effects of VPA on the metabolism of carnitine and ammonia. It would therefore seem advisable to monitor these parameters in epileptic children on long term antiepileptic treatment.