Epilepsy Study Links Antiseizure Drugs to Different Risks During Anticoagulant Treatment

A large international study has raised important questions about how antiseizure medication selection may affect adults with epilepsy who are also taking direct oral anticoagulants (DOACs), a widely used group of blood-thinning medicines.

The research found that outcomes differed depending on which antiseizure medication was used alongside a DOAC. Levetiracetam and strong enzyme-inducing antiseizure medications were associated with higher thromboembolic risk, while valproate was associated with higher mortality and major intracranial bleeding compared with a reference group receiving lamotrigine or lacosamide.

The findings are particularly relevant because epilepsy and conditions requiring anticoagulation can coexist in the same patient, creating a complex prescribing situation in which seizure control, prevention of blood clots and bleeding risk all need to be considered together.

What Did the Epilepsy and Anticoagulant Study Examine?

Researchers investigated the comparative safety of commonly used antiseizure medications in adults with epilepsy who were receiving direct oral anticoagulants. The study used real-world electronic health record data from an international healthcare network.

The investigators used a target-trial emulation approach, a research method designed to reproduce some features of a randomised clinical trial using observational healthcare data. This allowed researchers to compare outcomes between different antiseizure medication groups while attempting to account for differences between patients.

The broader database included more than 2.29 million adults with epilepsy. Of these, 40,932 were eligible for direct oral anticoagulant treatment, while 9,529 treatment initiators were included in the final analysis.

The mean age of participants was 63 years, and 51% were female. Researchers compared levetiracetam, valproate, moderate enzyme-inducing antiseizure medications and strong enzyme-inducing antiseizure medications with a pooled reference group receiving lamotrigine or lacosamide.

Key Findings From the Study

The results showed that different antiseizure medication groups were associated with different clinical outcomes among people taking direct oral anticoagulants. Differences were observed in thromboembolic events, major bleeding and overall mortality.

Levetiracetam Associated With Higher Thromboembolic Risk

One of the most notable findings involved levetiracetam, a commonly prescribed antiseizure medication.

Among patients receiving a DOAC, levetiracetam was associated with nearly twice the risk of thromboembolic events compared with the pooled lamotrigine or lacosamide reference group. The reported hazard ratio was 1.98, with a 95% confidence interval of 1.37 to 2.87.

Levetiracetam was also associated with higher all-cause mortality. The reported hazard ratio for mortality was 1.60, with a 95% confidence interval of 1.23 to 2.08.

Importantly, researchers did not find an increased risk of major bleeding with levetiracetam in this comparison.

The finding is significant because levetiracetam is widely used in epilepsy and is often considered to have relatively few conventional drug interactions. The results suggest that the relationship between antiseizure medications and anticoagulants may be more complex than interaction checks based only on established metabolic pathways indicate.

Why Enzyme-Inducing Antiseizure Medicines Matter

The study also found an association between strong enzyme-inducing antiseizure medications and increased thromboembolic risk.

Strong enzyme-inducing medications were associated with a hazard ratio of 1.55 for thromboembolic events compared with the lamotrigine or lacosamide reference group. At the same time, these medications were associated with a lower risk of major bleeding, with a reported hazard ratio of 0.62.

This combination is important because changes in anticoagulant exposure could potentially influence both clotting and bleeding outcomes. However, the observed associations should not automatically be interpreted as proof that one medication directly caused another clinical outcome.

The findings highlight why medication selection in people taking multiple therapies requires consideration of the complete clinical picture rather than focusing on a single potential drug interaction.

Valproate Linked to Bleeding and Mortality Concerns

Valproate produced a different pattern of findings in the study.

Compared with the lamotrigine or lacosamide reference group, valproate was associated with higher all-cause mortality. The reported hazard ratio was 1.49, with a 95% confidence interval of 1.09 to 2.04.

The researchers also observed a substantially higher risk of major intracranial bleeding, with a hazard ratio of 3.01. The association was approximately three times as high in the analysed cohort, although the confidence interval was relatively wide because these events were less common.

Valproate was also associated with a higher risk of aspiration pneumonia, with a reported hazard ratio of 3.08.

These findings add another dimension to the medication-selection question. While some antiseizure medications in the study were primarily associated with thromboembolic outcomes, valproate showed associations involving mortality and serious bleeding.

Could Antiseizure Medication Choice Affect Stroke Risk?

The study may have implications for stroke prevention because thromboembolic events can include serious conditions such as ischemic stroke, systemic embolism and other blood-clot-related complications.

People receiving DOACs generally take these medicines because they have a significant reason to prevent blood clots. Common clinical situations include atrial fibrillation and other conditions associated with an increased risk of thrombosis.

If another medication is associated with a change in anticoagulant effectiveness or exposure, the consequences can be clinically important. A treatment strategy intended to reduce clotting risk could potentially become less effective in certain medication combinations.

However, the findings should be viewed as an important safety signal rather than evidence that every patient taking a particular antiseizure medication will experience a harmful outcome.

Why This Study Matters for Doctors and Patients

The significance of the research lies partly in its size and real-world design. Researchers were able to analyse thousands of treatment initiators across a large international healthcare network rather than relying on a small single-centre study.

The use of propensity score matching was another important component. Researchers matched treatment groups to create more comparable populations before assessing outcomes. This can reduce the influence of measured differences between patients, although it cannot eliminate every possible source of bias in observational research.

The study also included a negative-control analysis involving patients receiving vitamin K antagonists. The thromboembolic hazard ratios in that analysis were close to one, providing additional context for interpreting the main findings.

What Are Direct Oral Anticoagulants?

Direct oral anticoagulants are medicines used to reduce the formation of harmful blood clots. They include several commonly prescribed drugs and are frequently used in people with conditions such as atrial fibrillation or venous thromboembolism.

Unlike traditional anticoagulants such as warfarin, many DOACs do not require routine dose adjustment based on regular clotting-time testing. Their convenience has contributed to widespread use.

However, DOAC treatment still requires careful consideration of kidney function, age, other medications, bleeding risk and the underlying reason for anticoagulation.

When a patient also has epilepsy, antiseizure medication becomes another important factor in the treatment equation. The current research reinforces the importance of reviewing the entire medication list rather than considering each prescription independently.

Why Drug Interactions Can Be Clinically Important

Some antiseizure medications can influence enzymes or transport proteins involved in the processing of other medicines. Such effects can potentially alter the concentration or activity of a co-administered drug.

For anticoagulants, changes in drug exposure can have consequences in opposite directions. Too little anticoagulant effect may increase the risk of clotting, while excessive anticoagulant effect may increase bleeding risk.

This makes medication management particularly important for people who have multiple chronic conditions and take several medicines simultaneously.

Study Limitations Should Also Be Considered

Despite its large sample size, the research has important limitations. It was a retrospective observational analysis based on electronic health records rather than a randomised controlled trial.

Observational studies can identify associations but cannot always establish direct cause and effect. Differences between patients receiving different antiseizure medications may remain even after statistical matching.

Electronic health records can also contain incomplete information about medication adherence, disease severity, lifestyle factors and clinical decision-making. These factors may influence outcomes but may not be fully captured in the database.

The results therefore need to be interpreted alongside clinical trials, pharmacological evidence, prescribing guidance and individual patient circumstances.

What the Findings Could Mean for Future Research

The study could encourage additional research into the safety of specific antiseizure and anticoagulant combinations.

Future prospective studies may help determine whether the observed associations are caused by pharmacological interactions, differences in patient characteristics, differences in disease severity or a combination of factors.

Researchers may also investigate whether particular DOACs behave differently when combined with individual antiseizure medications. Such evidence could eventually help clinicians make more precise treatment decisions for patients who require both seizure prevention and anticoagulation.

What Patients Taking Both Medicines Should Know

Patients should not stop, switch or change the dose of an antiseizure medication or anticoagulant based on this study alone. Both types of medicine can be important for preventing serious complications, and sudden changes can carry their own risks.

Instead, patients taking both medications should ensure that their neurologist, cardiologist, physician, pharmacist or other prescribing professional knows about the complete list of medicines they use.

Any unusual bleeding, symptoms suggestive of a blood clot, sudden neurological changes or other serious symptoms require prompt medical attention.

A Broader Lesson About Epilepsy Treatment

The study highlights a broader issue in modern epilepsy care: seizure control is only one part of managing a patient with complex health needs.

As people live longer and develop multiple chronic conditions, neurologists increasingly need to consider cardiovascular disease, stroke prevention, kidney function, other medications and age-related risks when selecting antiseizure treatments.

This makes personalised medication review increasingly important. The best antiseizure medication is not necessarily determined by seizure type alone. Tolerability, other health conditions, potential interactions and the patient’s broader treatment plan can also influence the decision.

Conclusion

The large international cohort study suggests that antiseizure medication choice may be associated with meaningful differences in thromboembolic, bleeding and mortality outcomes among adults with epilepsy receiving direct oral anticoagulants.

Levetiracetam and strong enzyme-inducing antiseizure medications were associated with higher thromboembolic risk, while valproate was associated with higher mortality and major intracranial bleeding. These findings underline the importance of carefully evaluating medication combinations in patients who require both epilepsy treatment and anticoagulation.

The research does not mean that one medicine is universally safer than another, nor does it establish that the medications directly caused the observed outcomes. Instead, it provides evidence that antiseizure medication selection deserves particular attention when a patient is also receiving a DOAC.

For patients and healthcare professionals, the central message is clear: complex medication combinations require careful, individualised assessment, and treatment decisions should be made with qualified healthcare professionals rather than based on a single observational study.

Frequently Asked Questions

What did the epilepsy study find?

The study found that adults with epilepsy taking direct oral anticoagulants had different thromboembolic, bleeding and mortality outcomes depending on the antiseizure medication they received.

Was levetiracetam associated with higher blood clot risk?

Yes. Levetiracetam was associated with a higher risk of thromboembolic events compared with the pooled lamotrigine or lacosamide reference group.

Was valproate associated with bleeding?

Yes. Valproate was associated with a higher risk of major intracranial bleeding in the study, along with higher all-cause mortality and aspiration pneumonia.

Should patients stop their antiseizure medication?

No. Patients should not stop or change antiseizure or anticoagulant treatment without medical advice. Medication changes should be discussed with the appropriate healthcare professional.

Does the study prove that these medicines cause complications?

No. The research was based on observational electronic health record data. It identified associations but cannot establish definitive cause and effect.

Why is this research important?

The findings highlight the importance of considering potential medication interactions and the overall clinical profile when treating people who require both antiseizure therapy and anticoagulation.