How can antiepileptic drugs affect bone mass, structure and metabolism? Lessons from animal studies

Patients with epilepsy, treated with antiepileptic drugs (AEDs) are at increased risk of fractures. Although several commonly used AEDs reduce bone mass in patients, the mechanisms are only scarcely known. In this review, we focus on the usefulness of animal models to explore the skeletal effects of AEDs. Moreover, we report our findings from a recent study comparing the effect of levetiracetam (LEV), phenytoin (PHT) and valproate (VPA) on various aspects of bone health in actively growing female rats. Our data indicate that these AEDs act differently on bone mass, structure and metabolism. A novel finding is that LEV reduces bone strength and bone formation without altering bone mass. Based on these results we propose that epidemiological fracture studies of patients treated with LEV are needed, and that these patients should be evaluated regularly to identify possible bone-related side effects.