Predictors of bone density in ambulatory patients on antiepileptic drugs

Antiepileptic drugs are associated with bone loss and fractures. Data in children is scarce and the impact of new therapies and of low vitamin D is not clear. This study assessed predictors of bone mineral density (BMD) in 225 ambulatory patients with epilepsy.

BMD and detailed clinical information were obtained from 137 adults mean age of 31 years, on therapy for a mean of 11.7 years, and 88 children mean age of 13 years, on therapy for an average of 4.7 years.

Hypovitaminosis D was common in epileptic patients. BMD was reduced in adults but not children with epilepsy, by 0.3-0.6 SD depending on the skeletal site measured, compared to controls. Duration of treatment, but not vitamin D levels, was negatively correlated with BMD at the hip in adults. Bone density was reduced with the use of both enzyme and non-enzyme-inducing drugs, with both mono- and polytherapy, and was most severely reduced at the spine and hip with the use of enzyme-inducing drugs. In the multivariate analyses, polytherapy in children and duration of therapy and enzyme-inducing drugs in adults were independent predictors of BMD.

Antiepileptic drug therapy is associated with low bone density at clinically relevant skeletal sites, projecting into a possible doubling of fracture risk. Age, therapy duration, polypharmacy and the use of enzyme-inducing drugs were risk factors. Newer drugs may be associated with deleterious effects on bone. Skeletal monitoring with varying intervals, depending on the individual risk profile, is indicated.