CHICAGO -- Cocaine use can promote blood clotting, which may explain how the drug triggers heart attacks in its users, according to a new study.
Cocaine caused blood to thicken by increasing the number of red blood cells, and by triggering an increase in a protein that causes platelets to stick together, said Dr. Arthur Siegel, the study's lead author.
The "double whammy" can cause clotting that can lead to heart attacks and strokes, said Siegel, chief of internal medicine at McLean Hospital outside Boston.
"(Cocaine use) is even more dangerous than we had previously known," he said. "Every time a person uses it, it's like a little bit of Russian roulette."
A previous study, released in June, showed that cocaine users are 24 times more likely to have a heart attack during the first hour after taking the drug. The new study, which appears in Monday's issue of the Archives of Internal Medicine, may help explain why such heart attacks occur, Siegel said.
The study suggests that anticoagulants may be useful in treating cocaine-induced chest pains, Siegel said. And he said it provides further warning to athletes who might use cocaine or substances with a similar affect in an attempt to enhance performance.
Siegel acknowledged that the study's small sample size made the conclusions preliminary, and he suggested further study.
"We're very confident that both of these observations are real," he said.
The study measured changes in the blood in 21 people before and for 60 minutes after they sniffed a moderate amount of cocaine or received it intravenously. Red blood cell counts on average increased 4 percent to 6 percent after individuals ingested the drug, due to constriction of the spleen. Cocaine use causes the spleen to constrict, pumping more red blood cells into the system, Siegel said.
The thickened blood must circulate through already-constricted vessels, creating a potentially dangerous situation, Siegel said. Previous studies have shown that cocaine use causes blood vessels to narrow.
The study also found an average 40 percent increase in a blood protein known as the von Willebrand factor in subjects who received cocaine intravenously. The von Willebrand factor promotes clotting by causing platelets to stick together.
Dr. Steve Frohwein, a cardiologist and assistant professor at the Emory University School of Medicine in Atlanta said several factors -- such as infection, cancer or other toxins -- can lead to clotting.
"Cocaine just stimulates a well known cascade of events," said Frohwein, who was not involved in the study.