Pot Could Make Epileptic Seizures Worse: Study

By The Canadian Press
Source: Canadian Press

Toronto -- Some people who use marijuana to try to control their epilepsy could actually risk making their seizures worse -- if research showing the drug's effects on laboratory rats is any indication.
Scientists at the University of Saskatchewan have found that although a synthetic version of pot's active ingredient can suppress grand-mal seizures in lab rats, in some cases it may intensify the most common cause of convulsions, those which originate in the front of the brain.

Some people who can't tolerate the side-effects associated with standard medications to treat epilepsy -- from headaches and nausea to drowsiness and cognitive dysfunction -- turn to marijuana or synthetic forms of the psychoactive ingredient in cannabis, THC, to reduce the severity of seizures.

While previous studies had identified no adverse effects, new research led by Dr. Michael Corcoran at the University of Saskatchewan unexpectedly found that the pot compound can actually cause seizures in laboratory rats.

"What we found was contrary to our expectation in that although after a single injection there could be a suppression of seizure, when we gave the drug more than once to the rats over a period of days, their seizures actually got worse," Corcoran, a professor in the department of anatomy and cell biology, said Tuesday from Saskatoon.

Researchers are able to simulate epilepsy in rats through a process called kindling, in which tiny bursts of low-voltage current are administered over time. With repetition, the electrical discharge spreads from brain cell to brain cell, eventually creating a kind of firestorm of neural activity that resembles what occurs in human epilepsy.

Corcoran's team found that kindling gets worse when rats are injected with high doses of the marijuana-like drug. The doses were high enough that the rats also ended up stoned: some were immobile, had changes in muscle tone and their ability to walk a beam -- a measure of intoxication -- was affected, he said.

The long-term goal of such research is to figure out how a certain drug might work in humans, said Corcoran, who has been working in epilepsy research for about 30 years.

"Ultimately, it's always an empirical question," he said. "Do the effects of a drug in a rat predict the effect of that drug in a human being? For drugs that are useful in treating epilepsy, that's generally been the case."

Those effects also depend on the type of seizure, he said. With those that originate in the brain stem, located between the brain and the spinal cord, cannabis-like compounds have been found to suppress convulsions.

But "what our work suggests is that seizures that originate in the forebrain, particularly in the temporal lobe, probably are not the best candidate type of epileptic seizures to be treating with marijuana-like drugs."

While it's difficult to calculate the human equivalent of the doses given to the rats -- especially since street pot and reportedly even government-sanctioned medicinal marijuana can vary in strength from batch to batch -- Corcoran said the study's findings should possibly give pause to some people using cannabis for epilepsy.

"If I were a clinician and I had the option of using marijuana to treat seizures, I'd want to make very sure what kind of seizure type the particular patient was displaying, because some seizures might benefit from these drugs, but others might get worse," he said.

And for those with epilepsy who want to use weed to self-medicate?

"I would say, 'Make sure you don't take whopping big doses and be sensitive to the kind of epilepsy you have.'"

Source: Canadian Press
Published: Wednesday, August 11, 2004
Copyright: 2004 The Canadian Press