Reports of deaths or injuries related to drug treatments more than doubled between 1998 and 2005 in the United States, with painkillers and immune-system boosters accounting for most, researchers said on Monday.
"This study shows that substantially growing numbers of patients are experiencing serious injuries from drug therapy," they wrote in a report in the Archives of Internal Medicine.
"This growing toll of serious injury shows that the existing system is not adequately protecting patients and underscores the importance of recent reports urging far-reaching legislative, policy and institutional changes," they added.
Thomas Moore and colleagues at the Institute for Safe Medication Practices in Huntingdon Valley, Pennsylvania, said the findings came from a look at serious adverse drug events as reported to the U.S. Food and Drug Administration from 1998 through 2005.
A "serious adverse drug event" is one that causes death, birth defects, disability, puts someone in a hospital or was life-threatening.
The FDA gets information about such occurrences directly or from drug makers, who are required to report them. A bill pending in the U.S. Congress would force the agency to do more active surveillance, for instance, by checking insurance records.
The study found 467,809 such occurrences during the period studied, with annual reports growing from 34,966 at the start to 89,842 at the end. The number of deaths due to drugs jumped from 5,519 to 15,107 during the study period.
"The overall relative increase was four times faster than the growth in total U.S. outpatient prescriptions, which grew in the same period from 2.7 billion to 3.8 billion," the researchers wrote.
MORE PEOPLE, MORE DRUGS
The researchers estimated that a growing population and more intensive use of drug therapy might account for a quarter of the increase.
An additional 15 percent of the increase appears to involve newer biotech drugs such as interferons, which help the body's immune system attack viruses, bacteria and other invaders.
"Among the most frequently reported drugs associated with fatal events, we observed a disproportionate contribution of pain medications and drugs that modify the immune system," they added.
The FDA said the reason for the increase in reports is not completely known.
"While some of this has to do with the increasing number of prescriptions, there are clearly other factors responsible for this increase, such as the increase in public attention to drug safety, and use of the Internet to make it easier for the public to ... report adverse events to FDA," spokeswoman Sandy Walsh said in a statement.
Walsh said FDA has started a program to review the safety of some new drugs about 18 months after approval.
The agency has been under fire from consumer advocates and Congress for its record of approving drugs -- such as Merck and Co's arthritis drug Vioxx -- that are later shown to have dangerous side-effects. Vioxx was withdrawn in 2004 after being linked to strokes and heart attacks.
At the same time, cancer advocacy groups accuse the agency of being to slow or too strict about approving the use of experimental new therapies.