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Taking a closer look at AEDs and Osteoporosis 
by Sue Goss

As the National Epilepsy Awareness Campaign in 2004 has highlighted, epilepsy can affect women in unique ways. That goes for Antiepileptic Drugs (AEDs) as well. Given that women have to take medication to prevent seizures, what are the side-effects that can be expected and how can these be reduced?

Dr Sandra Petty, photo right, recipient of an Epilepsy Association Research Scholarship for 2004, is working at the University of Melbourne and the Royal Melbourne Hospital to test the effects of AEDs on bone density and, in the long term, the development of osteoporosis. The best way of doing such a study is with twins, one of whom is taking AEDs and the other who is not.

Why twins? Previous research in the area suggests that there may be some link between epilepsy or epilepsy medication and bone density: Studies in the USA show that elderly people on AEDs are more likely to fall and fracture but many studies have no adequate ‘control’ group. The power of a study is increased three to five-fold where a non-medicated twin of the same gender (or a sister close in age) is used as a control.

Although non-medical people might think that comparisons of studies could be made around the world, the reality is that the results are more reliable if the two people are measured on the same day and on the same bone densitometry machine.

‘The people being studied should be as similar as possible - if one is taking any other medication which affects bone density they can’t take part -we also consider other factors including exercise levels, calcium intake and body weight which need to be similar between the twin or sister pairs to be included in the study as these factors can also have an effect on bone density.

‘The study will test over a three year period. Preliminary bone density results have shown differences between the sisters at forearm, hip and lumbar spine. This is more pronounced, the longer the patient has been taking medication. We only need to scan the sisters every two or three years as we do not expect a high rate of change over twelve months. The twins get free updates on their osteoporosis rate and are referred to a specialist for treatment if shown to be at risk. We use both dual X-ray absorptiometry (DXA) scans and blood tests which determine the vitamin D and bone turnover markers.’

Some medication may create more side-effects than others but people with epilepsy may not be able to change, just because of a possible risk of a side-effect. Reduction in seizures is of supreme importance, alongside monitoring and prevention of side effects wherever possible. The good news is that osteoporosis can be treated through exercise, diet, vitamin D and calcium intake, and specialised medication, at any age. n