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Marihuana: Effects on Neuronal Excitability and Seizure Threshold

  • Elisabeth Gordon
  • Orrin Devinsky

Abstract

In the late 19th century, British neurologists found that cannabis had a limited role in epilepsy therapy. Cannabinoid receptors are found in the brainstem, limbic and neocortical areas that modulate seizure activity. The recent studies of the effects of THC, CBD, and related cannabinoids in animal models of epilepsy reveal that (1) the effects vary significantly in different models, in different species, and for the different derivatives; (2) the mechanisms by which the cannabinoids exert their anti-or proconvulsant effects is not well-defined; and (3) the effects of acute administration (e.g., increasing seizure threshold) may be followed, in certain models, by a rebound effect (e.g., decreasing seizure threshold).

No well-controlled studies have evaluated cannabinoids in the treatment of epilepsy patients. However, clinical anecdotes and single case reports suggest that marijuana may reduce seizure frequency or, conversely may provoke seizure activity in select cases, while in most instances it has no significant effect on seizure activity. Several clinical studies have examined the efficacy of CBD on seizure frequency. These studies found either some reduction in seizure frequency or no statistically significant reduction compared to placebo. The few epidemiological studies that have been conducted suggest that marijuana use may protect against seizures induced by illicit drugs such as heroin and cocaine. The limited evidence therefore suggest that marijuana and the cannabinoids may have antiepileptic effects in man, but these effects may be specific to partial or tonic-clonic seizures.

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In the late 19th century, British neurologists found that cannabis had a limited role in epilepsy therapy. Cannabinoid receptors are found in the brainstem, limbic and neocortical areas that modulate…

Marijuana and Epilepsy

Could a plant that was introduced to the United States by early settlers provide relief for people with epilepsy today? Marijuana (Cannabis sativa) has been grown in the United States since the early 1700s. Settlers brought the plant from Europe to produce hemp. Its use as a medicine was recorded in a reference book from 1850 titled “United States Pharmacopeia”.

According to a recent paper in The Journal of the International League Against Epilepsy (Epilepsia), marijuana was used to treat a variety of conditions in ancient China as far back as 2,700 B.C. They included:

There is also evidence it was used in medieval times to treat:

  • nausea
  • vomiting
  • epilepsy
  • inflammation
  • pain
  • fever

Marijuana was given the status of a “schedule 1” drug class in the U.S. in 1970. As a result, studying how safe and effective it is as a medicine has been difficult for researchers.

Many people suffering from epilepsy say marijuana stops their seizures, but there is little scientific evidence. Researchers must apply for a special license from the Drug Enforcement Administration in order to study marijuana. They need permission to access to a supply kept by the National Institute for Drug Abuse. These challenges have slowed research.

However, there have been a handful of studies conducted in the U.S. since 1970. Other studies, even some ongoing, have been done around the world.

The findings reveal that the most well-known active ingredient in marijuana, tetrahydrocannabinol (THC), is just one of a group of compounds which have medicinal effects. Another, known as cannabidiol (CBD), does not cause the “high” associated with marijuana. It is emerging as one of the plant’s leading medicinal compounds.

Based on these initial studies, there are many studies currently ongoing throughout the US and other countries that are trying to answer the question of whether a drug formulation of CBD can help control seizures.

Both THC and CBD are in a group of substances called cannabinoids. They bind to receptors in the brain and are effective against pain associated with conditions like multiple sclerosis and HIV/AIDS. By attaching to receptors, they block the transmission of pain signals. CBD binds to more than just pain receptors. It appears to work on other signaling systems within the brain and has protective and anti-inflammatory properties.

Exactly how it works in epilepsy isn’t fully understood. But there have been small studies that show the results of using CBD. Studies of mice published in Epilepsia have shown mixed results. While some found CBD was effective against seizures, others did not. This may be due to the way the drug was given, since some methods work better than others.

The idea of using the compounds found in marijuana to treat epilepsy is gaining appeal. Researchers must confirm its effectiveness, and solve the problem of strength and how to give it. Potency can vary widely from plant to plant. Inhaling the drug versus eating CBD can alter the strength as well.

While there is a mounting consensus among people with epilepsy that medicinal marijuana is effective, researchers caution that the side effects need to be better understood. It’s also not known how CBD might interact with other medications.

Like most anti-seizure medications, marijuana has been shown to affect memory. This might lead to missed doses, which can mean that seizures return. A study in the Proceedings of the National Academy of Sciences suggested that cannabis use in children can result in a measurable drop in cognitive abilities.

Side effects might also depend on how the drug is taken. Smoking it would pose a risk to the lungs, while eating it would not.

Talk to your doctor if you are suffering from epileptic seizures and are not responding to traditional treatments. They can explain your options and provide information about medical marijuana use if you live in a state that allows it.

There are still other options if your state has no provision law for medical marijuana. Your doctor can share the latest research news with you and help you determine if a clinical trial for new forms of treatment or therapy might be right for you.

Some people who suffer from epilepsy believe that marijuana stops their seizures. Two compounds found in the drug, THC and CBD, may have medical benefits.