Anti-epileptic drugs and bone health

Some medications for epilepsy can increase your risk of osteoporosis and broken bones.

The exact reason for this is not entirely understood. But it's thought that some anti-epileptic drugs alter the way vitamin D is broken down and used by the body. Vitamin D helps the body absorb calcium, which is essential for bones.

Anti-epileptic medications are more likely to affect the strength of your bones if:

• you are taking high doses of these drugs
• you have taken lots of different types of anti-epileptic drugs
• you have been taking them for many years.

Furthermore, the direct effects of anti-epileptic medications may also increase the risk of fall-related broken bones, by causing drowsiness and slowing down of the body’s protective reflexes, as well as affecting balance and coordination.

Do all anti-epileptic drugs cause osteoporosis?

Various studies have indicated a loss of bone density and increased risk of fractures in people using long-term anti-epileptic drugs.

Most of the research in this area has been in people taking the older anti-epileptic drugs such as:

• phenytoin (Epanutin)
• phenobarbital
• carbamazepine (Tegretol)
• primidone (Mysoline)
• sodium valproate (Epilim)

A drug safety update from the MHRA (the UK government agency that ensures medicines are acceptably safe) has reviewed the evidence (April 2009) and found that long-term treatment with:

• carbamazepine
• phenytoin
• primidone
• long-term treatment with sodium valproate

can reduce bone density which may lead to osteoporosis and broken in certain ’risk’ groups. Particularly at risk are:

• people immobilised for long periods
• those not getting enough calcium in their food and drink
• when there is insufficient exposure to sunlight to maintain adequate vitamin D levels.

Currently, there is only limited and conflicting research data from the studies of other or newer non-enzyme inducing anti-epileptic drugs, such as gabapentin, lamotrigine, topiramate and levetiracetam (Keppra) regarding their effects on bone.

The findings from two recent research studies suggest that most anti-epileptic drugs are associated with an increased risk of broken bones. One of these studies analysed the data from several individual pieces of research and the other focused on people aged 50 years and older taking anti-epileptic drugs. However more research is needed to evaluate the long term effects of these medications on bone health.

I take anti-epileptic drugs – do I need a bone density scan?

Bone density scans provide information about the strength of your bones and are generally indicated when the result is needed to help determine whether a drug treatment for osteoporosis would be beneficial.

Although there are no definitive recommendations for people with epilepsy, if you have been taking anti-epileptic drugs long term and especially if you have other risk factors (see below) it may be useful to discuss your possible risk of osteoporosis and fracture with your doctor.

The doctor will assess your need for a bone density scan based on your overall risk and refer you for a scan if necessary.

The importance of assessing fracture risk is included in a recent (2015) National Guideline on the ‘Management of Osteoporosis and the prevention of fragility fractures’ from SIGN (Scottish Intercollegiate Guidelines Network) and recommends that people with epilepsy over the age of 50 who are taking anti-epileptic drugs (particularly the enzyme inducing type) and especially those with additional risk factors should be considered for fracture risk assessment.

Your bones will be less strong as you move into older age, whatever your bone density result, so you are more likely to need scanning and ‘assessment of fracture risk’ after the age of 50 years.

I take anti-epileptic drugs – do I need an osteoporosis drug treatment?

The main aim of an osteoporosis medication is to reduce the risk of broken bones.

Treatments will usually be recommended if it is considered that your risk of fracture is high. You risk is assessed based on a combination of factors such as your age, personal and family history of fractures, lifestyle factors such as alcohol use and smoking as well as information about bone density - if a scan has been performed.

Again, your risk of breaking a bone is higher in later life so you are more likely to be offered a drug treatment after the age of 50 years.

You may be prescribed a vitamin D supplement with or without an osteoporosis drug treatment to ensure you are getting sufficient vitamin D. A calcium supplement may also be recommended if you are not getting enough calcium in your diet.

Should my vitamin D level be checked?

The NICE (National Institute for Health and Care Excellence) guideline (2012) on the management of epilepsy in adults and children recommends checking vitamin D levels and undertaking any other investigations that may be appropriate to assess bone health every 2-5 years for all adults who take enzyme inducing anti-epileptic drugs.

However all current UK guidance suggests considering vitamin D supplementation in people who are felt to be at ‘higher risk’ (see above) including those taking sodium valproate or any of the enzyme inducing anti-epileptic drugs on a long term basis. The usual dose of vitamin D is 10-20 micrograms (mcg) or 400-800 international units (IU), although some doctors may prescribe higher doses.

What else can I do to prevent osteoporosis?

Factors which can help to maintain healthy bones are:

• a well-balanced diet with adequate calcium rich foods
• regular weight-bearing exercise but taking care to exercise within your capabilities particularly if you have any balance problems or physical disability
• avoiding smoking and keeping alcohol consumption within the recommended limits.

I take gabapentin for back pain caused by spinal fractures – could this make my osteoporosis worse?

Anti-epileptic medications such as gabapentin (Neurontin) can also be used to help with pain. If shape changes to the spine are severe as a result of spinal fractures, spinal nerves can get pinched or trapped resulting in neuropathic (nerve) pain. These drugs work by damping down the nerve signals going to your brain, so pain messages aren’t transmitted so effectively.

There is no conclusive research evidence to suggest that either gabapentin or another commonly prescribed medication, pregabalin, have any significant effects on bone when used for the indication of neuropathic pain.

The above medicines will always be started in low doses and increased gradually until an effective minimal dose is achieved to help manage your pain. Additionally when anti-epileptic medications are prescribed for pain they tend to be used for shorter periods compared to the long-term use of these drugs in people with epilepsy, which in itself constitutes a risk factor for bone health.

It’s always important to weigh up risks and benefits when taking any medication, but if gabapentin is making a difference and reducing your pain, then this benefit (based on current evidence) far outweighs any potential risk to your bone health.

Content reviewed: September 2017

(Updated: December 2021)