Blood Test for Marijuana Elusive
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Blood test for marijuana elusive By SALLY REESE Times Medical Writer Blood testing for marijuana is not going to be as "clear-cut" as it is for alcohol. That was the conclusion drawn from a study by LSU Medical Center investigators testing mari-juana's effect on psychomotor performance. The purpose of the study was to determine if impaired psychomotor performance — the ability to perform a task that requires head and hand coordination, such as driving a car or operating a complex industrial machine — was relative to blood levels of THC, the psychoactive agent of marijuana. The LSUMC team found that impaired performance lasts for at least two hours after smoking just one marijuana cigarette, but it was unable to correlate that to the drug's concentra-tions in the blood. "There's no way to do it," said Dr. Joseph E. Manna, research sponsor. "The blood levels rise and decline very rapidly, but even when they drop to zero, there is impaired performance." This is significant from both a medical and a forensic standpoint, said the chief of the toxicology section in LSUMC's Pharmacology Department. It means that researchers "probably will continue looking for ways to provide a meaningful in-terpretation of blood levels" in determining if a person is under the influence of marijuana, he said. Principal investigator of the study was Kenneth E. Ferslew, then a graduate student working on his doctoral degree. Dr. Ferslew, now with Quillan- Dishner Medical School in Johnson, Tenn., de-veloped the Pursuit Meter II that was used in the ; study. i The Pursuit Meter II is a device for testing human pursuit-tracking performance with com-puter- generated problems that can be correlated to everyday tasks. Pursuit-tracking is following a moving target and getting as close to the target as possible. Twelve college-educated men were assigned to problem patterns after smoking a marijuana joint calibrated to deliver various concentrations of THC, or none at all. (They smoked three joints, two with different amounts of THC, one with the THC removed.) Blood pressure, heart rate and pursuit-tracking performance were measured and blood was drawn for THC analysis.
|Title||Blood Test for Marijuana Elusive|
Louisiana State University Medical Center (Shreveport, La.)
Manno, Joseph E.
Ferslew, Kenneth E.
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|Source||Louisiana State University Health Sciences Center Shreveport Medical Library (http://lib.sh.lsuhsc.edu)|
|Coverage-Spatial||Shreveport (Caddo, La.)|
|Rights||Physical rights are retained by Louisiana State University Health Sciences Center Shreveport. Copyright is retained in accordance with U.S. copyright laws.|