Cannabinoids, and in particular Cannabidiol (CBD), have gained traction in the medical field as potential antiepileptic agents. A few widely mediatized cases of patients who recovered partially from what were previously intractable syndromes, together with positive results from preclinical research in animals and surveys of self-medicating patients, have paved the way for proper clinical trials.
However, preliminary results were mixed, suggesting that CBD could be effective for some cases, but not for others. This is probably attributable to epilepsy not being a single condition, but an amalgam of neurological symptoms that can arise from widely different disorders. After a first “blind” approach, researchers began planning clinical trials for specific epileptic conditions in an attempt to pinpoint which patients respond the most to CBD.
To this end, U.S. researchers recently conducted a CBD open label clinical trial with tuberous sclerosis complex (TSC) patients. The work was led by Dr. Elizabeth Thiele from the Massachusetts General Hospital in Boston, and the final results can be found in the medical journal Epilepsia.
TSC is a dominant non-sexual genetic disease that causes tissue malformation from an early age. Its symptoms vary widely, depending on which organ systems are affected. Considering neurological impairments alone, it is estimated that 85% of TSC patients develop epilepsy, of whom 63% are treatment resistant.
Eighteen patients with ages ranging from 2 to 31 were recruited for the trial. In addition to their normal antiepilepsy medication, the patients were given a daily dosage of 5 mg/Kg CBD that was increased every week up to a maximum of 50 mg/Kg daily. Overall, the weekly seizure frequency declined from baseline during the 12 months of treatment (changing from 22 seizures in median to 14.9 after two months and 7.7 after 12 months). Patients who were taking clobazam responded much better to CBD, suggesting a positive interaction effect.
Seven patients experienced seizure aggravation during the trial, but for six of them this was solved after adjusting the daily medication dosage of CBD and other antiepileptic drugs. By the end of the study, they were also experiencing less weekly seizures, as were the remaining 11 patients. Parents or physicians reported behavioral, cognitive and social gains in several patients (10 of the 18 patients were autistic and 6 of the 18 patients were confirmed to have cognitive impairments at the start of the study).
Although more than half of the patients did not show up for the 12 month follow-up, there is no evidence that this was due to a seizure aggravation. Twelve patients experienced adverse effects during the trial, the most common of which were drowsiness, ataxia and diarrhea. These tended to be temporary or manageable with adjustment of drug dosage. Of the three patients who formally quit the trial, only one was due to adverse side effects. According to the authors, no patient left the study because of CBD inefficacy.
The results from this trial are seemingly positive. Despite the small sample size and the non-blinded, uncontrolled design, the fact that most patients experienced a decline in seizure frequency and related cognitive and behavioral impairments is striking. All patients had failed to respond to previous treatments, which included a median of 7 antiepileptic drugs, together with an array of dietary therapies, surgeries, and nerve stimulation techniques. Larger controlled trials are now needed to confirm the potential mitigating effects of CBD for tuberous sclerosis complex epilepsy.
Authors’ conflict of interests: The leading researcher, Elizabeth Thiele, has served as a paid consultant for GW Pharmaceuticals.