Steady cocaine use linked to seizures.

Steady cocaine use linked to seizures

When moderately strong doses of cocaine are repeatedly given to rats, a considerable number of the animals develop lethal convulsions, according to scientists who spoke at an Alcohol, Drug Abuse and Mental Health Administration seminar last week in Washington, D.C.

"Our studies suggest that this 'kindling' process [in which convulsions are promoted by repeated consumption of the same dose] might easily mislead users into thinking they are taking a safe dose when, in fact, they are gradually lowering their brain's threshold for seizure and sudden death," said Robert Post of the National Institute of Mental Health, who reported the data along with colleague Susan Weiss.

The researchers first confirmed earlier reports that cocaine kindles seizures. About 40 percent of the rats they studies developed convulsions in the week after daily cocaine injections began. Either the first or second seizure resulted in death.

Cocaine is both an amphetamine-like stimulant and an anesthetic, says Post. To determine whether the anesthetic property kindled seizures, the researchers gave the rats equal doses of the local anesthetic lidocaine. Again, seizures rapidly developed, but the animals did not die. Post suggests that while the anesthetic properties trigger the seizures, cocaine's stimulant properties or interactions between stimulant and convulsive effects result in lethal convulsions.

The stimulating effects of cocaine on rats' behavior, such as hyperactivity and repetitive sniffing, were also increased by prior treatment with both lidocaine and amphetamine, notes Post, indicating that the drug's anesthetic and stimulant properties are both involved. Furthermore, a familiar environment significantly intensified behavioral responses to cocaine. Rats injected in the same test cage showed much more hyperactivity than rats given identical doses first in one test cage and then in another.

Individual responses to cocaine vary among both humans and rats, says Post, and not everyone develops an uncontrollable craving for the drug. But many people do not stop using cocaine once they start, and, he notes, "even if there is no dose escalation, one becomes more vulnerable to seizures over time. The point is, there's no safe dose."