|Vol. 20, No. 8||May 1, 1998|
UT-Houston Study Focuses on Cocaine Users
by SANDRA HENRY
The University of Texas-Houston Health Science Center
A two-part study of cocaine users conducted at The University of Texas-Houston has revealed in unprecedented detail how the drug affects blood flow in the brain, and how changes which can lead to stroke may be prevented. The investigation is the first in the U.S. to employ a form of brain scanning which enables physicians to accurately determine where and to what extent the brain's blood supply is compromised.
Researchers led by Dr. Bankole Johnson, associate professor and director of the Clinical Laboratory and Experimental Alcohol Research Program at UT-Houston Medical School, department of psychiatry & behavioral sciences, used a novel PET scanning technique - Single Photon Emission Computed Tomography (SPECT) - to measure blood flow within 20 regions of the brain during drug-taking. Cocaine use was found to cause significant reductions in blood flow, a common cause of stroke, particularly in regions rich in the brain chemical dopamine. Regions with comparatively little dopamine did not experience a marked change. This finding, together with an observed correlation between size of cocaine dose and the degree to which blood flow was reduced, suggests a link between the chemical dopamine and cocaine-induced stroke.
In the second phase of the investigation, the drug isradipine, a vasodilator which animal studies have shown prevents damaging reductions in brain blood flow, was administered to study participants one hour before the dose of cocaine. The effects of isradipine are believed to be most pronounced in regions rich in dopamine, which in phase I had been associated with marked reductions in blood supply during cocaine use. Quantitative SPECT imaging revealed that isradipine protected the brain against the potentially stroke-inducing changes in blood flow.
Dr. Johnson explains: "Not only was there no evidence of reduced brain blood flow in this instance, but some dopamine-rich areas fared significantly better with the cocaine + isradipine pretreatment than with a placebo, actually experiencing enhanced flow compared with the normal state.
"This is the first demonstration in humans that any medication can prevent the damaging effects of cocaine on brain blood flow. The results suggest that isradipine may be a useful therapeutic agent for cocaine addicts, many of whom are at high risk of stroke with all its attendant consequences for the individual and the health system. Further, this new quantitative SPECT technique, with its ability to give us a far more detailed picture of the pattern of blood flow, could prove useful in studying other vascular disorders of the brain, benefiting people in the U.S. and across the world."
The novel SPECT scanning procedure employed by the investigators features the capture of images by a Gamma Camera with a field of view large enough to record blood flow within the aorta and the head simultaneously, permitting measurement of the time taken for blood to reach particular areas of the brain. This capability, combined with the use of an improved radioactive tracer substance, enabled the researchers to take far more accurate measurements than is possible with the standard qualitative SPECT imaging method.
The two-part study, published in the April issue of Neuropsychopharmacology (Part I), and in the April 11 issue of Psychopharmacology (Part II), was conducted in collaboration with Dr. Lamk Lamki, professor and chief at UT-Houston Medical School division of nuclear medicine. Funding was provided by the Advanced Technology Program of Texas.
Data from the Drug Abuse Warning Network (DAWN), which collects data on drug abuse morbidity and mortality, shows increases in adverse health consequences associated with the use of cocaine. In 1991, the number of cocaine-related ER incidents began an increasing trend that reached an estimated 142,410 in 1994 from a low of 80,355 in 1990. In 1995, the National Household Survey on Drug Abuse found an estimated 1.5 million Americans were using cocaine; over a third of these on a frequent basis. Cerebrovascular accidents are a common cause of death among cocaine addicts.
©2006 Texas Medical Center