News

Doctors warned to be wary of new drugs

Deborah Josefson, Nebraska

Doctors should be wary of starting their patients on newly approved drugs, because of the high rate of adverse side effects that go undetected until late in the post-marketing surveillance period, a new study says (JAMA 2002;287:2215-20[Medline]).

More than 10% of new drugs approved by the Food and Drug Administration (FDA) have serious side effects that are not discovered on initial testing and marketing, says the study, led by Dr Karen Lasser and Dr Paul Allen of the Department of Medicine at Cambridge Hospital in Cambridge, Massachusetts.

The investigators analysed 548 drugs approved by the FDA from 1975 to 1999. The list of drugs was obtained from an online database of drug approvals maintained by the Tufts University Center for the Study of Drug Development.

Only drugs defined as new molecular entities not previously marketed in the United States were included in the study. Drugs sold over the counter, diagnostic agents, and biological products were excluded. However, prescription drugs that became available over the counter during the study period were included.

The researchers used the Physicians' Desk Reference, an annual guide to prescription drugs, as a measure of developments in changes to labelling of adverse reactions, and they used the Federal Register and the FDA's website to compile a list of drugs withdrawn for safety reasons.

They found that over 10% (56/548) of all new chemical entities approved from 1975 to 1999 acquired a new "black box warning"indicating a serious adverse reaction that may result in death or serious injuryor were withdrawn from the market. Sixteen drugs (3%) were withdrawn and 45 (8.2%) required one or more new black box warnings.

Half of the withdrawals occurred during the first two years after the drug's introduction, and half of the new black box warnings occurred during the first seven years. Thus in 50% of the drugs an adverse reaction went undetected until relatively late in the course of a drug's appearance.

One of the drugs, terfenadine (marketed in the United States as Seldane), a popular non-sedating antihistamine, was on the market for 13 years before being withdrawn. Another, cisapride (marketed in the United States as Propulsid), which was approved as an aid to prevent gastrointestinal reflux, was available for six years before withdrawal. Both were withdrawn because of their risk of causing arrhythmia.

The study found that the probability of a new drug acquiring a black box warning or of being withdrawn from the market over 25 years was 20%.

The authors said that these results were conservative, as they did not include information from such sources as letters to doctors containing drug information. They blamed the high prevalence of adverse drug reactions on aggressive marketing techniques by drug makers, rapid approvals by the FDA, and faulty post- marketing surveillance systems.

They advise that "clinicians should avoid using new drugs when older, similarly efficacious agents are available" and that "patients who must use new drugs should be informed of the drug's limited experience and safety record" and be closely observed.

Seldane was withdrawn after 13 years because of the risks of causing arrhythmia