Introduction

Epilepsy is a common brain disorder, about a third of epilepsy patients suffer drug-resistant epileptic seizures. Cannabis has been used in the treatment of epilepsy for thousands of years but has only recently been legalised for medical use.¹ In recent times CBD based medications like Epidyolex have been approved for those with drug-resistant epilepsy.^1,2 However, the side effects of this treatment should be fully understood. 

There are lots of CBD oils being sold, however, the quality and content of these products is unknown.³ A recent study aimed to see how much CBD was actually in over the counter products. Only 38% of products were close to the advertised CBD content. There was also a presence of controlled substances within these products for example THC and cannabinol, as well as other controlled substances were detected in 55% of over-the-counter CBD products.⁴ This highlights the importance of being aware of the potential side effects if you purchase any over the counter or online products. 

How CBD work for epilepsy?

Overview of CBD and the brain

Researchers support the use of CBD as a treatment for epilepsy, however they have been unable to understand the exact mechanisms underlying its anti-seizure effects. CBD is characterised by several different activities and has been shown to have effects such as anti-inflammatory, protection against neuronal loss, normalising neurogenesis and acting as an antioxidant , which contributes to CBD’s anti-seizure effects.⁵ Studies have found that seizures were reduced by 33% following treatment with CBD.⁶ 

Popular CBD-based medications

Epidyolex is a purified liquid which contains CBD oil and has been approved in the UK and the US for the treatment of epilepsy.^3,8 It is commonly used in rare types of epilepsy syndrome known as Lennox-Gastaut syndrome and Dravet syndrome. Epidyolex will not get you ‘high’ as it does not contain THC.³ 

Common side effects of CBD

Do CBD oils like Epidyolex cause side effects, and what are they? 

It is possible to develop side effects when using medical CBD such as:

• Decreased appetite 
• Diarrhoea 
• Nausea 
• Weakness 
• Mood changes 
• Dizziness
• Fatigue
• Feeling high
• Hallucinations 
• Suicidal thoughts

Side effects associated with CBD such as fatigue may interfere with daily activities like school, or work. Gastrointestinal issues such as diarrhoea may affect patients' quality and life. Furthermore, changes to appetite can lead to weight fluctuations which may also affect individuals quality of life.⁸ 

Less common but notable side effects

Liver enzyme elevation

In some cases, CBD oil-based medications like Epidyolex may cause transaminase elevation.⁸ Transaminase is an enzyme that can be an early sign of liver stress or damage.⁹ This uncommon side effect is more commonly seen in those receiving high daily doses.¹⁰ Liver enzyme elevation is less common when using over the counter products as they have lower doses of CBD.¹¹ 

Mood and behavioral changes

Epidyolex has also been shown to affect mood.³ Mood changes can have significant social and economic effects including functional impairment, disability, lost work productivity, and increased use of health services. These socioeconomic effects can lead to reduced quality of life for patients affected.¹² 

Interactions with other medications

Potential drug interactions

Another potential issue is polypharmacy (the use of multiple medications) to treat the same condition may lead to drug interactions that limit how well the drug works or increase the side effects of another drug.¹³ It is important to work with your healthcare provider when using medications like Epidyolex to monitor any side effects that may occur. 

Long-term considerations

Unknowns of long-term use

Although short-term side effects are now better understood, long-term effects especially in children need more research and there are some things we do not yet know, and further research is required to fully understand long-term side effects.¹⁴ This highlights the importance of working with a healthcare provider to monitor any long-term side effects that may occur such as signs of liver dysfunction when using CBD oils for extended periods of time.⁸ 

Managing side effects

Working with a healthcare provider

You may need to lower your dose of medication to reduce the effects of CBD oil based medications.¹⁵ It is important to work closely with your healthcare provider to find the optimum dosage for you. 

Tips for reducing side effects¹⁶

• Starting with a low dose and gradually increasing may reduce the risk of side effects such as nausea
• Eating five small meals as opposed to three large meals may help to reduce nausea symptoms 
• Avoid drinking large amounts of liquids and drink slowly to avoid triggering nausea 
• Allow your stomach to settle after meals and avoid vigorous activity for at least 30 minutes but do not lie down after eating

Summary of benefits vs. side effects

While CBD-based medications may offer promising results for epilepsy treatment, particularly in drug resistant cases, patients and caregivers should be aware of potential side effects.³ CBD’s exact mechanism in seizure reduction isn’t fully understood, however, it has shown a range of beneficial effects.⁵ Despite this adverse reactions, including gastrointestinal issues, mood changes, and liver enzyme elevation, highlights the need for careful monitoring.⁸ The long-term impacts of CBD remain largely unknown and require further research. To reduce side effects, a gradual increase in dosage under healthcare supervision is recommended, along with lifestyle adjustments.¹⁶ Working with healthcare providers can help optimise CBD treatments, minimise risks, and improve quality of life for those managing epilepsy with CBD.