Abstracts

Previous studies have shown that use of antiepileptic drug (AED) therapy is a risk factor for osteoporosis and fractures in postmenopausal women. Data in males is scarce. One of the leading theories for this problem is an AED-induced enhanced metabolism of vitamin D. Several AEDs induce the metabolic capacity of the CYP450 system, specifically the isozyme 3A4, which is involved in the degradation of active vitamin D. It is thought that chronically decreasing the level of active Vitamin D induces a secondary hyperparathyroidism with elevated parathyroid hormone levels and low calcium levels. The 3A4 enzyme-inducing AEDs include phenytoin, phenobarbital, carbamazepine, oxcarbazepine and felbamate. Our objective was to determine if 25-hydroxy Vitamin D[sub]3[/sub] (25-OH-D[sub]3[/sub]) levels, parathyroid hormone (PTH) levels, and calcium levels differ between male patients taking enzyme-inducing AEDs (EIAEDs) and those taking non enzyme-inducing AEDs (NEIAEDs)., We examined 25-OH-D[sub]3[/sub], intact PTH, and calcium levels in 210 male veterans attending an out-patient seizure clinic (age range: 20-89; mean: 58). Patients had a mean duration of AED therapy of 20.3 ([plusmn]1.40) years. We divided the patients into two groups: those taking at least one EIAED for at least the last six months (n=126) and those taking only NEIAEDs for at least the last six months (n=64). Patients taking divalproex sodium were analyzed separately (n=20)., Statistical analysis showed significant differences in 25-OH-D[sub]3[/sub], intact PTH, and calcium levels between EIAEDs and NEIAEDs (see [italic]Table[/italic]). Minor influences of increasing patient age, increasing duration of AED therapy, and specific AED were also observed., Patients taking enzyme-inducing AEDs for seizure disorder have a significantly lower level of Vitamin D[sub]3[/sub] and calcium, and a significantly elevated level of PTH compared with patients taking non enzyme-inducing AEDs. These levels are consistent with a secondary hyperparathyroidism suggesting that the enzyme-inducing AEDs negatively affect Vitamin D levels and possibly their metabolism. This fact suggests that these male patients may need supplementation with vitamin D to avoid osteoporosis.[table1],