To characterize the effect of three different doses of vitamin D3 supplementation on serum 25-hydroxyvitamin D (25(OH)D) changes in epilepsy patients receiving enzyme-inducing antiepileptic drugs (EIAEDs) versus patients receiving non enzyme-inducing antiepileptic drugs (non-EIAEDs), and to determine the prevalence of and risk factors for hypovitaminosis D among Thai patients with epilepsy.

A single-blinded prospective, randomized study undertaken at epilepsy clinic of King Chulalongkorn Memorial Hospital. The patients with hypovitaminosis D were included and divided into two groups according to the type of AEDs use. Patients receiving each AEDs type were randomly assigned to receive vitamin D3 1000, 3000 or 6000 IU once daily. The mean increment in serum 25(OH)D levels were measured at 8 and 16 weeks.

Inclusion Criteria:

• Epilepsy patients, age ≥ 15 years, BMI18 - 30 kg/m2
• Being treated with either enzyme inducing antiepileptic drugs (EIAEDs: phenytoin, phenobarbital, carbamazepine and topiramate) or non-enzyme inducing antiepileptic drugs (Non-EIAEDs: sodium valproate, levetiracetam, and lamotrigine) at a stable dosage regimen for at least a year.
• Serum 25(OH)D <30ng/ml

Exclusion Criteria:

• Patients with a history of hypercalcemia, nephrolithiasis, fractures, hepatic disease, kidney disease, granulomatous disease or currently supplemented with vitamin D.