‘Safe’ Doses of Cocaine Tied to Fatal Seizures : Study Finds That Chronic Use of Drug Lowers Brain’s Ability to Fight Off Attacks and Death
Repeated doses of an amount of cocaine that is initially safe can produce potentially fatal seizures even if the dosage is not increased, according to results of tests on laboratory animals disclosed Wednesday by the National Institute of Mental Health.
Chronic cocaine use, institute researchers said, makes the brain more susceptible to such seizures and could even cause the condition to occur when the drug is not being taken.
Calling cocaine “exceedingly unpredictable,” Dr. Robert Post, who directed the study, described a process termed “kindling,” by which the brain becomes increasingly sensitive to the drug.
Most Unaware of Process
“Anyone who has one cocaine-related seizure should consider never taking another dose,” Post said. Because most users are unaware of this process, he said, they might be misled “into thinking they are taking a safe dose when, in fact, they are gradually lowering their brain’s threshold for seizure and sudden death with each snort or toke.”
“Some of the behavioral and toxic properties of cocaine in response to some (specific) dose . . . increase over time,” Post said. “It’s not an accumulation of the drug; it’s an increase in responsiveness to the same dose over time.”
The study, which sought also to determine which qualities of the drug are responsible for different types of responses, linked cocaine-related seizures and other sensory and cognitive alterations with the drug’s anesthetic properties and attributed cocaine-induced euphoria to the drug’s stimulant properties.
Marijuana Tied to Aging
Another study released Wednesday at a forum of the Alcohol, Drug Abuse and Mental Health Administration showed that chronic use of marijuana may produce changes in the brain similar to the changes that accompany the aging process.
The marijuana study, conducted by Dr. Philip Landfield, of Wake Forest University’s Bowman Gray School of Medicine, reports that laboratory rats injected with tetrahydrocannabinol, known as THC, the active ingredient in marijuana, five times a week for a period of eight months showed a significant decrease in nerve cell density in the hippocampus, the segment of the brain that plays an important role in emotional behavior and is clearly affected by aging.
Light and electron microscopy of this area of the brains of rats subjected to repeated injections of THC showed substantive changes in the cells similar to the changes produced by the normal aging of the brain.
Researchers said that those changes mimic the effects of adrenal steroids, hormones believed to be associated with the aging process.
Definite Links Not Found
“We’re still testing the hypothesis that these hormones affect the aging of the brain, so it’s another step away to say marijuana affects the aging process,” Landfield said. “We have not definitely linked these kind of anatomical changes with behavioral changes.”
The study showed that cell density decreased about 20% in areas of the brains of young rats injected with THC. Older rats that were not injected with the chemical showed decreases of about 30%. The concern, said Marvin Snyder of the National Institute on Drug Abuse, is the effect of the combined losses of brain density.
“If a young adult has a 10%, 20% or 30% loss early in life, it might go undetected. But, as one gets older, the combined effect of the loss could be as much as 60%,” Snyder said.
