Calcium metabolism serum markers in adult patients with epilepsy and the effect of vitamin D supplementation on seizure control.

PURPOSE: To evaluate serum markers of calcium metabolism in adult patients with epilepsy (PWE) treated with antiepileptic drugs (AEDs) and the effect of vitamin D supplementation on seizure frequency.

METHODS: Serum levels of calcium, phosphate, intact parathyroid hormone (iPTH) and 25-hydroxyvitamin D (25[OH]D) were compared in 160 PWE on chronic therapy with AEDs and 42 matched controls. Blood concentrations were analyzed taking into account the different features of epilepsy and treatment. Finally, the effect of vitamin D supplementation on seizure control was assessed in a subgroup of 48 drug resistant epileptic patients.

RESULTS: PWE showed lower serum levels of 25[OH]D compared to control subjects (p < .001). Only 25% PWE showed normal 25[OH]D levels, whereas 41,9% had a vitamin D failure and 33,1% a vitamin D deficiency (p < .001). 25[OH]D serum levels depended on treatment duration, number of medications and enzyme-inducing AEDs (p < .001, p < .001, p = .013, respectively). Polytherapy and enzyme-inducing AEDs showed more detrimental effects on the 25[OH]D and calcium serum levels. The administration of vitamin D failed to significantly improve seizure control.

CONCLUSIONS: PWE show deficiency of vitamin D. The serum levels of 25[OH]D depend on the features and duration of AEDs treatment. Vitamin D administration in drug resistant epilepsy patients does not result in a reduction of seizure frequency.