Expert advice for prescribing cannabis medicines

Approximately 75% – 90% of individuals with TSC will have epilepsy at some point in their lives.  There is renewed interest in the therapeutic benefits of cannabis medications, especially for individuals affected by treatment-resistant epilepsy, however clear prescribing guidelines for cannabis medicines in drug-resistant epilepsy are scarce.

This study, authored by a multi-disciplinary team in Australia outlines prescribing advice for using cannabis medicines in patients with epilepsy.

About this research

This study was put together by a working group of Australian specialists, clinical pharmacists, pharmacologists and cannabis researchers.  It addresses the gap between practice and research when it comes to prescribing cannabis medicines for individuals with paediatric and adult epilepsy.

The authors use their clinical experience as well as evidence from research to provide a consensus for prescribing cannabis medications.  This study reports on different types of epilepsy, whether symptom relief was achieved and side effects. The authors also discuss the different cannabis medicines available, as well as dosing and drug interactions.

Applicability to patients with TSC

Approximately 1-2% of the population has epilepsy.  In about one third of these, standard treatments fail to adequately control seizures.  In TSC, where seizures are a common neurological feature, up to half of people affected will have treatment-resistant epilepsy.

In the past 5 years a number of studies have examined the use of cannabis medicines in patient populations with epilepsy arising from a number of conditions, including TSC.  All of these studies demonstrated reduced seizure frequency associated with cannabis medications.  Specifically, in both adult and paediatric TSC there was a significant reduction in the average frequency of seizures by 49%.  Based on this, the authors have suggested that people with TSC are eligible for treatment with cannabis medicines if:

• They have a clinical diagnosis of TSC that is not controlled by standard anti-seizure medication;
• They are more than 1 year of age;
• They have a minimum of 8 seizures per month on average over a 3-month period.

The report also lists exclusion criteria for treatment with cannabis medicines and details the regulatory issues associated with prescribing these medicines.

Important points to note

• There are only 2 cannabis medicines approved and subsidised by Australian government regulatory agencies for medical prescription.
• These medications are often very expensive if not approved on the PBS.
• There are significant risks from non-regulated, artisanal or homegrown cannabis products.
• Effectiveness and side effects are still being researched.
• Cannabis products in saliva or blood testing may pose a problem in occupational and roadside driving drug screening.
• Common side effects reported in clinical trials include: diarrhoea, sleepiness, decreases in appetite and weight.
• Regular liver function testing is required as cannabis medicines can cause liver toxicity.
• Cannabis medications can interact with other medications, including epilepsy medications and mTOR inhibitors (this is a very important and under recognised issue).

Outcomes of this research

This study provides medical practitioners with evidence-based guidelines to assist them in prescribing cannabis medications in treatment resistant epilepsy, and outlines important considerations for clinicians who prescribe these medications.

John Lawson, Terry O’Brien,Myfanwy, Graham,Elianne, Renaud,Dean Jones, Jeremy Freeman, Nicholas Lawn,  Jennifer H. Martin (2022). Expert advice for prescribing cannabis medicines for patients with epilepsy – drawn from the Australian clinical experience.

Full text available (free of charge) at: https://bpspubs.onlinelibrary.wiley.com/doi/10.1111/bcp.15262

Please also see the interview between TSA and Dr John Lawson about the trial of add-on cannabidiol (CBD) treatment for drug-resistant seizures in TSC at  https://tsa.org.au/cbd-trialdrjohnlawson/

DISCLAIMER

This information is intended to provide some insights into recent TSC-related research.  It is not intended to, and it should not, constitute medical or other advice.  Readers are warned not to take any action without first seeking medical advice.