An extract of marijuana shows promise as a treatment for children with severe epilepsy who have been unresponsive to other treatments, after an early-phase safety study is presented at the American Academy of Neurology's annual conference.

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Is there more to marijuana? Clinical trials are trying to find out.

The study is an analysis of early clinical trialing, so mainly designed to be the first test of the potential medicine's safety and tolerability for patients as well as its possible effectiveness. The extract under investigation is cannabidiol (CBD), and was taken in a liquid form once daily.

Across 10 medical centers, the study took in a series of open-label trials, so there was no placebo control - the fact of an investigational drug being given was known to both medical staff and participants.

A total of 213 children and young adults, with a middle-average age of 11 years, received the extract. There is no "high" from pharmaceutically produced CBD because it is not the part of the plant with psychoactive properties.

All the children had severe forms of epilepsy - including Dravet and Lennox-Gastaut syndromes, which can mean lifelong disabling seizures - and their conditions had not responded to other treatments. They received the experimental treatment under the FDA's expanded access program, which makes investigational drugs available for testing to people with serious or life-limiting conditions.

The results provided so far - and to be presented at the American Academy of Neurology's annual meeting, which starts at the end of this week in Washington, DC - give only the relative reductions in numbers of seizures suffered by the participants - there was a decrease in these during the study of around half.

Only future phases of clinical trialing could test effectiveness properly - using greater numbers of patients in randomized controlled trials, which will also help to reduce the effects of bias.

Between the start and finish of at least 12 weeks of treatment, the number of seizures across the combination of small trials fell by:

  • 54% overall
  • 53% for convulsive seizures among the small total number of people, 23, with Dravet syndrome
  • 55% for atonic seizures (sudden loss of muscle tone) in the 11 people with Lennox-Gastaut syndrome.

Against the safety measures, out of the 213 children enrolled, 137 completed the full 12 weeks, and side effects included:

  • Drowsiness (affected 21% of participants)
  • Diarrhea (17%)
  • Tiredness (17%)
  • Decreased appetite (16%).

For 12 people, reported side effects led them to stop trying the experimental drug.

Study author Dr. Orrin Devinsky, of New York University Langone Comprehensive Epilepsy Center, confirms the seizure reductions observed represent early findings, and that larger, placebo-controlled, double-blind trials are needed.

Dr. Devinsky says there have been few formal studies of the marijuana extract, adding:

"These results are of great interest, especially for the children and their parents who have been searching for an answer for these debilitating seizures."

From illicit drug to potential prescription products

This early investigation of medical marijuana for epilepsy comes on the back of animal studies and case reports. Dr. Devinsky appeared in a report in May 2014 - when he introduced his work on CBD and epilepsy.

Dr. Devinsky said: "While cannabis has been used to treat epilepsy for centuries, data from double-blind randomized, controlled trials of CBD or THC in epilepsy is lacking. Randomized controlled studies of CBD in targeted epilepsy groups, such as patients with Dravet or Lennox-Gastaut syndromes, are in the planning stages."

Tetrahydrocannabinol - THC - is another marijuana extract and, like CBD, it is also the subject of much interest.

The later-stage trials of CBD that Dr. Devinsky hopes for in epilepsy may now be possible, and would be commercially funded by GW Pharmaceuticals, sponsor of the present phase trial. The pharma company has half a dozen marijuana-based candidates for therapy, in a number of disease areas beyond epilepsy, including multiple sclerosis.

Pharmacology information from the company says CBDs have a diversity of potential uses, because they may "exert many of their pharmacological effects by interacting with, and modulating, the human endocannabinoid system," which comprises a family of receptors.

Dr. Devinsky writes about marijuana in medicine in another article published this month in the journal Neurosurgery. "The first documented use in epilepsy may be from Assyrian clay tablets from the 7th century BCE," and it was the late 1980s when scientists found that THC exerts its effects by binding to two cell membrane receptors: "the cannabinoid type 1 (CB1) and type 2 (CB2) receptors."

In an overview of the real-world clinical evidence that has been gathered so far for medical marijuana used to treat neurological disorders, the American Academy of Neurology states that it is not yet known if marijuana will prove helpful in epilepsy. The 2014 systematic review concludes:

"For patients with epilepsy, data are insufficient to support or refute the efficacy of cannabinoids for reducing seizure frequency."