Cannabis and the treatment of epilepsy

Epilepsy affects 1.5% of the world population. One third of those affected suffers from what is known as refractory epilepsy, that is, epilepsy that does not respond to conventional treatment.

Patients suffering from refractory epilepsy have often unsuccessfully tried controlling their seizures with different types of medication (from 3 to 5 or more antiepileptic drugs and steroids), as well as other treatments such as a ketogenic diet, vagus nerve stimulation and even surgery. Patients often have to endure the side effects of these treatments in addition to the harm caused by the underlying disease.

This means that a significant proportion of patients with epilepsy have no satisfactory therapeutic response, and some have to put up with tens or even hundreds of seizures every day. Many such cases never reach adulthood.

The use of cannabis in treating seizures –one of the clinical forms of epilepsy– has been documented throughout the history of medicine, going back thousands of years.

In our time, the use of cannabis and particularly cannabidiol (CBD) in the treatment of epilepsy, has become more widespread as the result of the findings of preclinical and clinical research. There are also multiple accounts of significant improvements in different unclassified types of epilepsy that are difficult to control and in the context of Dravet, Lennox-Gastaut, Doose and West syndromes.

Anticonvulsant action of CBD in the treatment of epilepsy

This was one of the first actions of CBD to be described by researchers in the 1970s and 1980s.

The mechanism or mechanisms of action by which CBD acts are not fully understood, but it is known that in the presence of CDB, levels of anandamide –one of the endogenous cannabinoids– increase.

Interactions of CBD with other antiepileptic pharmaceuticals

It is important to take into account the interactions of CBD with other antiepileptic pharmaceuticals, since it can increase the effect of some of these (e.g. phenobarbital) by inhibiting their destruction, and interfere with that of others (chlordiazepoxide and ethosuximide, for example). It is therefore important to watch for the appearance of adverse effects, which might be due more to the lack of inactivation of the antiepileptic drugs than the CBD itself. This is not to say that CBD does not have unwanted effects, but these are mild to moderate and diminish rapidly with changes in dose or removal of the treatment.

When the use of CBD is incorporated in the treatment of epilepsy, conventional medication should not be abruptly halted. Instead, the dose should be reduced slowly and under medical supervision as improvements are observed or the adverse effects of the accumulation of drugs are seen.

Effects of CBD in the treatment of epilepsy

Amongst patients being treated with CBD (whether or not it is administered in association with other antiepileptic pharmaceuticals), a significant percentage –generally above 50%– see a reduction in the number of seizures, to the point of ending them altogether. Improvements have also been shown in other aspects, such as at an emotional, cognitive and motor level, as well as in socialisation.

Finally, there are some cases of epilepsy that do not respond satisfactorily to the use of cannabis in treatment. In these situations, it may be necessary to add THC. This must be carried out carefully as it can either relieve seizures or trigger them, a phenomenon which tends to be dose-dependent.