Recognizing, Reporting, and Reducing Adverse Drug Reactions

South Med J. 2001;94(4) 

In This Article

Drug Testing

One reason for ADRs is the inability to identify them during product testing. There are a number of inherent and potentially avoidable problems with drug testing. The first problem is size. Usually 2,000 to 3,000 patients are involved in testing for any given drug.[1] Only ADRs occurring in 1:1,000 patients are detected; 16,000 patients would be needed to have an 80% likelihood of identifying all ADRs occurring in 1:10,000 people. The second problem is exclusion. Patients with complicated medical histories are often excluded from drug trials because efficacy is easier to establish this way. Also, pediatric and geriatric patients are often excluded from trials for similar reasons. The third problem is lag. Adverse drug reactions occurring with long-term use cannot be detected. Many fatal effects are discovered after a medication is approved, during postmarketing surveillance. During this time, the medication is introduced to a larger number of patients who often have more concomitant illnesses than the original study group.

Postmarketing surveillance has its own series of pitfalls, as well. One problem is the structure of the FDA, which is responsible for monitoring drugs after they have been approved. The vast majority of FDA staffers work on approving new drugs, and a much smaller percentage work on monitoring approved drugs in the Office of Post-Marketing Drug Risk Assessment.[14] Furthermore, this office reports its findings to the division of the FDA that approves new drugs, rather than acting independently. Another major problem is that surveillance is based on anecdotal reporting. According to the FDA, only about 1% of adverse events are reported.[15] Finally, it is not clear that new warnings issued by the FDA are heeded by physicians. After the FDA warned against using class IC antiarrhythmics for PVCs, a large percentage of physicians continued to prescribe them to patients already receiving treatment.[16]


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