Vitamin D Status in Children on Anticonvulsant Therapy

Objective To assess vitamin D status of children on long-term anticonvulsants, including the less studied widely used levetiracetam, and the potential risk factors for deficiency. Method Children on antiepileptic drugs (cases, n = 269) were compared with controls (n = 295) for serum biochemistry, 25OHD, parathormone (PTH), sun exposure, dietary calcium, and vitamin D intake. Results Cases had lower serum 25OHD [median (IQR) 18.4 (11.5-24.1) ng/mL] compared to controls [20.8 (15.4-26.2] ng/mL, p < 0.001), as well as more frequent vitamin D deficiency (25OHD < 12 ng/mL, 27.1%) and insufficiency (25OHD < 20 ng/mL, 57.6%) than did controls (11.2% and 46.1%, respectively). Significantly lower median (IQR) serum calcium [8.8 (8.1-9.4) vs. 9.2 (8.5-10.0) mg/dL], phosphorous [3.8 (3.3-4.2) vs. 4.7 (4.0-5.3) mg/dL), and higher PTH [58.4 (42.9-85.8) vs. 38.9 (24.6-55.5) pg/mL, p < 0.001 for all] and proportion of elevated alkaline phosphatase (11.2% vs. 5.1%, p < 0.01) was seen in cases versus controls. Vitamin D deficiency was present in 53.4% of children with cerebral palsy (CP) versus 19.9% in those without CP (p < 0.001). Serum 25OHD did not differ between patients on cytochrome P450 inducers versus noninducers, neither among the 3 major groups, users of carbamazepine, valproate, and levetiracetam. Logistic regression analysis showed serum 25OHD < 12 ng/mL to be independently influenced by case or control status, presence of CP, and season of sampling. Conclusion Vitamin D deficiency is common with anticonvulsant therapy, especially in those having CP. In Kerala, the hot, dry season from March to May is protective.