Deaths from medication mistakes at home, like actor Heath Ledger's accidental overdose, rose dramatically during the past two decades, an analysis of U.S. death certificates finds.

The authors blame soaring home use of prescription painkillers and other potent drugs, which 25 years ago were given mainly inside hospitals.

"The amount of medical supervision is going down and the amount of responsibility put on the patient's shoulders is going up," said lead author David P. Phillips of the University of California, San Diego.

The findings, based on nearly 50 million U.S. death certificates, are published in Monday's Archives of Internal Medicine. Of those, more than 224,000 involved fatal medication errors, including overdoses and mixing prescription drugs with alcohol or street drugs.

Deaths from medication mistakes at home increased from 1,132 deaths in 1983 to 12,426 in 2004. Adjusted for population growth, that amounts to an increase of more than 700 per cent during that time.

In contrast, there was only a five per cent increase in fatal medication errors away from home, including hospitals, and not involving alcohol or street drugs.

Abuse of prescription drugs plays a role, but it's unclear how much. Valid prescriptions taken in error, especially narcotics such as methadone and oxycodone, account for a growing number of deaths, said experts who reviewed the study.

The increases coincided with changing attitudes about painkillers among doctors who now regard pain management as a key to healing. Multiple prescription drugs taken at once — like the sleeping pills, painkillers and anxiety drugs that killed Dark Knight star Ledger — also play a part, experts said.

"When we see overdoses, we're seeing many more mixed drug overdoses," said Dr. Jeffrey Jentzen, president of the National Association of Medical Examiners and director of autopsies at the University of Michigan in Ann Arbor. Jentzen said autopsies are much more likely to include toxicology tests today than 25 years ago, which would contribute to finding more fatal medication errors as cause of death.

But Phillips said there were no significant increases in other poisonings like suicidal overdoses or homicides, so more testing doesn't explain the huge increase. The analysis excluded suicides, homicides and deaths related to side-effects.

Alcohol, street drugs often a toxic brew

The increase was steepest in death rates from mixing medicine with alcohol or street drugs at home; that death rate climbed from 0.04 per 100,000 people in 1983 to 1.29 per 100,000 people in 2004.

Many patients ignore the risk of mixing alcohol with prescriptions, said Cynthia Kuhn of Duke University Medical Center, who was not involved in the study.

"They think, 'Oh, one drink won't hurt.' Then they have three or four," Kuhn said.

The increase in deaths was highest among baby boomers, people in their 40s and 50s.

"We're sort of drug happy," said boomer Dr. J. Lyle Bootman, the University of Arizona's pharmacy dean, who was not involved in the research. "We have this general attitude that drugs can fix everything."

People share prescriptions at an alarming rate, Bootman said. One recent study found 23 per cent of people say they have loaned their prescription medicine to someone else and 27 per cent say they have borrowed someone else's prescription drugs.

Kenneth Kolosh, a statistics expert at the National Safety Council, praised the study, but said improved attention to coding location on death certificates may account, in part, for the huge increases the researchers found.

Phillips countered that home deaths from any cause increased relatively little during the time period, so better coding doesn't explain the change.

Michael Cohen, president of the Institute for Safe Medication Practices, said more states should require pharmacists to teach patients about dangerous drugs and insurers should pay pharmacists to do so.

There were over 45,000 adverse reactions to medication reported in Canadian hospitals outside of Quebec in 2006-07, according to the Canadian Institute for Health Information. In other words, about 22 out of every 1,000 people were hospitalized because of such a reaction.