According to a study released on Wednesday, more than three percent of "sudden deaths" in a region of Spain, and probably across much of Europe -- are related to cocaine use.
Even modest amounts of the illegal drug cannot be considered safe for so-called "recreational use," the authors warned, noting that cocaine consumption has risen sharply in recent years in Europe.
Twenty-one out of 668 sudden deaths reported in the southwestern part of Spain during 2003 to 2006 were linked directly to cocaine, said the study, published in the European Heart Journal.
Most of these fatalities were due to heart or cardiovascular system problems.
The findings can be extrapolated to the rest of Spain and other countries that have similar levels of drug use, the researchers said.
"As the estimated number of European young adult cocaine consumers is similar in Spain, Britain and Italy, there is no reason to consider that the cocaine-related sudden death would be different to what we have found in southwest Spain," said Joaquin Lucena, a researcher at the Institute of Legal Medicine in Seville.
"The notion that recreational cocaine use is 'safe' should be dispelled, since even small amounts may have catastrophic consequences, including sudden death," Lucena, the study's leader, said in a press release.
There are some 12 million adult Europeans who use cocaine, with more than five percent of the population in the same three countries reporting usage at least once -- 7.7 percent in Britain, 7.0 in Spain and 6.6 in Italy.
The researchers called for systematic blood and urine tests in sudden death cases to more accurately assess the role drug abuse plays in premature deaths.
Until this happens, "the prevalence of cocaine and other illicit drug use will be underestimated, and cocaine-related complications will not be recognised," they conclude.
In a separate commentary in the same journal, David Hill and Richard Lange, professors at the University of Texas, agree that usage figures are probably significantly higher than indicated by the study.