Neurological

Does CBD Help Seizures? Examining the Evidence for CBD as an Antiepileptic

does cbd help seizures

Epilepsy often prevents patients from living a normal life. Even with advanced interventions like vagus nerve stimulation via implanted medical devices, patients are still liable to be wracked by unpleasant and frightening seizures at any time. If they occur frequently, these seizures can preclude patients from driving, working, and living independently. Additionally, patients are often left suffering under the burden of their therapy’s side effects and some side effects—like somnolence and fatigue—can often be just as debilitating as the seizures they are meant to prevent. Nonetheless, even therapies that fail to resolve symptoms to an adequate degree can provide some limited relief, so patients continue to take them.

Today, however, a growing number of patients are turning to a powerful therapy that has been proven effective in the context of treatment-resistant epilepsy: cannabidiol. Cannabidiol (CBD) is a chemical derived from the leaves of the hemp plant, which has a history of human use going back thousands of years. CBD has been the subject of intense scientific research owing to relatively recent discoveries which indicate that CBD has the potential to modulate neuronal activity. Significantly, researchers have found that CBD is not overtly psychoactive, unlike other constituents of the cannabis plant, most notably tetrahydrocannabinol (THC). Because CBD isn’t intoxicating or habit-forming, its ability to modulate neuronal activity makes it appealing to many people struggling with epilepsy.

Scientific investigations into CBD’s antiepileptic potential have quickly borne fruitful findings for patients. With a recent systematic review of clinical trials claiming that 48% of patients exhibited a 50% reduction in the frequency of their seizures after CBD therapy, there is a strong base of evidence in favor of using CBD as an antiepileptic. If patients are still not experiencing remission of their seizures as a result of their current therapeutic regimen, there is a very real chance that they will benefit from trialing CBD therapy.

How Does CBD Affect the Neural Basis Of Epilepsy?

CBD’s impact on epilepsy is difficult to understand without familiarity with the neural basis of seizures. When neurons in the brain are activated by an electrochemical signal, they transmit their own electrochemical signal to another neuron. The strength of the outgoing signal is dependent on the strength of the signal that the neuron receives. Under normal conditions, neurons experience a brief refractory period after they have been activated. This prevents them from repeatedly activating at full strength; subsequent re-activations will not produce as strong of an activation from the recipient neuron until it has recovered from prior activations. And even if a neuron is being over-activated, it is still regulated by other groups of neurons which will detect the over-activation and, subsequently, inhibit it. As a result, neurons normally do not become activated simultaneously, strongly, and repeatedly, even if they are in the same area of the brain and serve the same function.

Under the conditions of extreme over-activation, however, the normal safeguards are overwhelmed. Seizures are caused by repeated synchronous strong activation of groups of neurons; when the neurons are activated strongly, simultaneously, and repeatedly, this activation cascades to the rest of the brain, temporarily overwhelming the inhibitory circuits. The wave of synchronized over-activation displaces the normal patterns of activation that are responsible for maintaining homeostasis, disrupting function. Eventually, this cascade arrives at one of the brain areas responsible for the visible signs of seizures, typically in the temporal lobes. The activation in these areas then causes the stereotyped motions and muscle clenching associated with seizures.

To control seizures, CBD molecules inhibit neurons’ ability to activate by binding to two of the cannabinoid receptors, CB1 and CB2. Though the mechanism by which binding of CB1 and CB2 inhibit neuronal activation is still under study, researchers believe that CBD enables neurons to control their level of calcium, which is necessary for neuronal activation. Rather than simply decreasing the level of intracellular calcium, researchers found that CBD improves neurons’ ability to sequester excess calcium and also their ability to access stored calcium when deficient. Because neurons can’t activate as strongly or as quickly with a modulated calcium balance, the inhibitory neural circuits remain in control, and normal patterns of activation can persist.

The Challenges of Conventional Treatments

CBD mode of action differs in significant ways from other therapies. For example, benzodiazepines also inhibit neurons’ ability to activate but do so via a different mechanism. With the benzodiazepines, the level of inhibition is much higher because the drug molecules bind directly to GABA (gamma-aminobutyric acid) receptors rather than CBD receptors. Binding to the CBD receptors causes a moderation of the neuron’s’ ability to activate, but it does not directly engage inhibitory neural mechanisms in the way that GABA does. The difference is akin to taking a foot off of the gas (CBD) versus pumping the brakes (benzodiazepines and other GABA-targeted therapies). The consequences of this higher level of neuronal inhibition are sleepiness, reduced motor coordination, slurred speech, sluggish thought, lowered social inhibitions, and amnesia, all of which can significantly compromise quality of life and even personal safety.

Additionally, benzodiazepines are notorious for building both physical and psychological dependency as a result of their anxiolytic properties. Tolerance can build extremely quickly, meaning that patients will often stop experiencing benefits at the dose they were prescribed, causing them to seek more and potentially resulting in addiction. Furthermore, benzodiazepine class drugs cause neurons to exhibit a rebound effect wherein neuronal activation is higher than normal following the drug’s clearance from the brain. This rebound effect most often manifests in patients as anxiety, although secondary seizures caused by cessation of antiepileptic treatment and subsequent rebound activation may also occur. Finally, the addictive nature of benzodiazepines makes them unsuitable for long-term treatment of seizures in most cases.

Other antiepileptics include carbamazepine and its analogues, phenytoin, phenobarbital, valproate, gabapentin, and lamotrigine. Most of these drugs operate by increasing the concentration of GABA at the synaptic cleft via a handful of different mechanisms. The impact and side effects of these drugs vary considerably as a result of their differing mechanisms, however. Some, like phenobarbital, share many overlapping side effects with the benzodiazepines. Others, like valproate, have a different side effect profile altogether in which patients experience bleeding, anemia, nausea, and depressed mood.

Not all antiepileptic drugs utilize GABA concentrations as their primary mechanism, however. In contrast to the GABA-enabling drugs, carbamazepine and phenytoin block the sodium channels on neurons. This prevents them from initiating the repetitive activation characteristic of seizures but does not result in systemic inhibition in the way that the GABA-enabling drugs do. Patients taking these drugs may struggle with blurred vision and low blood pressure as a consequence. Gabapentin, on the other hand, operates by tuning the calcium channels on neurons, causing transient dizziness, sleepiness, and unexpectedly aggressive behavior. By altering the calcium channels, neurons are less able to rapidly recover the ability to send a strong signal after activation. Thus, the over-activation seizure state is less likely to occur. As powerful and as diverse as these drugs may be, however, patients with epilepsy may still have seizures even when taking several different medications.

CBD has a distinct advantage over many other therapies for epilepsy not only due to the novel mechanism of action, but as a result of its low side effect profile and lack of dependency risk. This makes it appealing for a broad range of patients struggling with epilepsy, giving them the ability to effectively address symptoms in a way other treatments do not while optimizing quality of life and minimizing the potential of new dangers.

CBD Is Effective Against Treatment-Resistant Epilepsy

While the relative safety and tolerability of CBD make it highly attractive to many, CBD therapy is also exciting because it has been shown to ameliorate epilepsy symptoms even when other interventions have failed. For the 74 patients from a study of five Israeli pediatric epilepsy clinics, CBD therapy may have been life-changing. In the study, all of the patients selected for analysis experienced daily seizures despite trials of 8 or more antiepileptic drugs. If CBD therapy was successful within this cohort, researchers posited that it would make for an effective adjunct treatment which might give patients relief before the last resort therapies were necessary. The majority of these patients were under age 12, and all were under age 18. In each of the five clinics, patients received varying doses of CBD over different intervals of time. Because each clinic had its own methods, there was no unified study protocol, but rather a handful of different clinical practices being implemented piecemeal in an attempt to help patients when other interventions failed.

Nonetheless, CBD succeeded where the others had failed. In fact, 89% of patients with treatment-resistant epilepsy experienced a lower frequency of seizures once they started CBD therapy. Of these patients, 18% claimed that their seizures nearly or totally disappeared with the help of CBD therapy. Another 34% of the patients experienced a 50% reduction in the frequency of their seizures, and an additional 12% reported lesser but still significant reductions. These impressive results suggest that most patients with epilepsy will experience a substantial improvement in their symptoms with the help of CBD therapy. Though larger clinical trials with adult epilepsy patients are still needed to characterize the most effective therapeutic regimen, the results of the Israeli study are extremely promising and have been replicated in a slightly older cohort by an independent group of researchers.

Of course, CBD—like other therapies—does have the potential for side effects. Patients who take CBD sometimes experience daytime sleepiness, excessive fatigue, or gastrointestinal disturbances, which are sometimes enough to make patients discontinue CBD therapy. According to the summary of the Israeli trials, as many as 7% of patients in the study experienced a worsening of their seizures after starting CBD therapy, although no causal relationship has been established. For most patients, however, there will be few side effects of CBD therapy. Nonetheless, experimentation with CBD should be performed with the help of a medical professional and started gradually.

CBD Is Revolutionizing Epilepsy Therapy

In light of the numerous pieces of overwhelmingly positive evidence in favor of using CBD therapeutically, the antiepileptic therapy landscape today is drastically more favorable for patients than that in prior years. And there is reason to believe that this landscape will continue to improve; scientific interest in CBD therapeutics for epilepsy of all types is growing at a rapid pace, and new studies are increasing the level of understanding that clinicians have regarding what CBD can do for patients. While there is strong evidence that CBD may be highly beneficial for patients with treatment-resistant epilepsy, research is increasingly indicating that CBD has the potential to be an excellent first-line treatment for epilepsy as well. Given the extensive side effect profile of traditional antiepileptics, CBD will soon become a mainstream therapy, helping patients improve quality of life and potentially allowing them to replace their current regimen of antiepileptics.

Patients need not wait for any of the forthcoming clinical trials regarding CBD therapy to begin to address their symptoms. A plethora of CBD products intended for therapeutic use are already on the market, and more are soon to arrive. Clinical protocols for CBD therapy are still forming, but the abundance of evidence suggests that patients may benefit from 10-20 mg/kg of 99% CBD oil and 1% propylene glycol administered on a daily basis. As a result of the recent publications and positive press coverage of CBD therapeutics, patients struggling with epilepsy will likely find that their doctors are amenable to helping them with a trial of CBD therapy.

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Works Cited

Devinsky O, Marsh E, Friedman D, Thiele E, Laux L, et al. 2016. Cannabidiol in patients with treatment-resistant epilepsy: an open-label interventional trial. The Lancet Neurology 15:270–278. https://www.ncbi.nlm.nih.gov/pubmed/26724101

Elphick MR, Egertova M. 2001. The neurobiology and evolution of cannabinoid signalling. Philosophical Transactions of the Royal Society B: Biological Sciences 356:381–408. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1088434/

Ryan D, Drysdale AJ, Lafourcade C, Pertwee RG, Platt B. 2009. Cannabidiol targets mitochondria to regulate intracellular Ca2+ levels. Journal of Neuroscience 29:2053–2063. http://www.jneurosci.org/content/29/7/2053

Stockings E, Zagic D, Campbell G, Weier M, Hall WD, et al. 2018. Evidence for cannabis and cannabinoids for epilepsy: a systematic review of controlled and observational evidence. Journal of Neurology, Neurosurgery & Psychiatry 89:741–753. https://www.ncbi.nlm.nih.gov/pubmed/29511052

Tzadok M, Uliel-Siboni S, Linder I, Kramer U, Epstein O., et al. 2016. CBD-enriched medical cannabis for intractable pediatric epilepsy. Seizure 35:41–44. https://www.seizure-journal.com/article/S1059-1311(16)00005-4/fulltext

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