There is a desperate need for randomised trials on the use of medical cannabis in drug-resistant epilepsy in adults,  an expert has told the ANZAN 2018 conference in Darwin.

Speaking during a symposium dedicated to medical cannabis Professor Terry O’Brien, Director of Neurology at Alfred Health in Melbourne, noted that much of the hype around the use of medical cannabis has centered on children with epilepsy.

“But about a third of our adult patients don’t have control with our current epilepsy medications and they are desperate for a solution… they are incredibly keen to engage in this space…and many… have a strong feeling that their self administered cannabis has an important role in controlling their epilepsy,” he told delegates.

Professor O’Brien said there was a long history of anecdotal reports of the efficacy of cannabis as an anti-seizure treatment.

“This is not a new idea… if you go right back to the 1880s the famous British neurologist Sir William Gowers reported the case of an adult in his 40s who had drug-resistant epilepsy which was not well controlled by bromides but when tried on a cannabis based mixture became seizure free,” he said.  

However evidence of its use in adults with poorly controlled epilepsy was lacking. While there was now class 1 evidence from double-blind placebo randomised controlled trials for cannabidiol (CBD) transdermal gel  as adjunct treatment to anti-epileptic drugs in severe epileptic encephalopathies, only a small proportion of patients in these trials were adults.

The ZYN2-CL-03 STAR 1 and 2 studies were the first double blind RCT of CBD treatment for adults with drug resistant focal epilepsy.

The STAR 1 trial, of which Professor O’Brien was the principal investigator,  showed that changes in seizure frequency was not significantly different between ZYN002 (transdermal gel)  and placebo.

However, continued open-label treatment in STAR 2 appeared to result in improvements in seizure control  with clinically meaningful reductions observed after six and 12 months of treatment. The transdermal gel was also well tolerated with good patient compliance.

In addition to the need for more evidence, Professor O’Brien told delegates that he believed  red tape and cost were two other significant barriers to prescribing medical cannabis.

“The red tape is a nuisance but it’s not insurmountable. There are two ways you can prescribe medical cannabis in Australia, you can do it the way we do it for all drugs that are not TGA licensed drug for this indication [SAS Individual Approvals], and by the way none of the CBD products are for epilepsy at this stage, or you can get registered through the TGA as an authorised prescriber”.

According to Professor O’Brien, however, cost to the patient was the biggest problem. Pharmaceutical grade CBD for an adult of around 70 kg on a 20mg dose per day could be as much as $6,000 a month based on figures he had obtained from a supplier.

“There are some small governmental schemes that will subsidise the cost for some children but there’s no help for adults – the cost has to be borne by the patients themselves,” Professor O’Brien said.  

“It beholds us to encourage companies who want to market a drug in this space to go through the effort of doing proper evidence-generating randomised controlled trials and then applying to the TGA to get the drug registered and then on to the PBS.”

“That’s the only way it’s going to become widely available for our patients,”he added.