More Side Effects in Newer Drugs
Prior to Food and Drug Administration (FDA) approval, possible adverse drug reactions are often determined in limited populations over short time periods. Pharmaceutical companies also often publicize drugs before all side effects are known.
As a result, many new drugs may be approved without full knowledge of adverse reactions. In addition, it is estimated that less than 10% of adverse drug reactions are reported to the FDA after a drug has hit the market.
This study determined the relationship between new prescription drug releases and the addition of "black box warnings" (warnings required by the FDA, to be placed on drug packaging, that indicate potentially severe, life-threatening adverse events associated with a particular medication) or removal from the market. The authors examined the Physicians' Desk Reference - the FDA guide to drug-labeling information - for all new drugs approved from 1975-1999 and all drugs withdrawn from the market for safety reasons from 1975-2000. The results of the study are listed below:
* An estimated 20% of prescription drugs received a black box warning or were removed from the market after release to the public in the 25-year period of the study.
* Half of changes to drug warning labels occurred within seven years of introduction.
* Half of withdrawals from the market took place within two years of introduction.
According to the authors, the FDA should raise the threshold for approving new drugs when alternative drugs or therapies are available. They stress, "The safety of new agents cannot be known with certainty until a drug has been on the market for many years."
Lasser KE, Allen PD, Woolhandler SJ, et al. Timing of new black box warnings and withdrawals for prescription medications. Journal of the American Medical Association
2002:287(17), pp. 2215-2220.