When a new drug enters clinical trials, special attention is given to older adults (65 years or older) because they often develop unwanted effects to drugs at levels that are well-tolerated by younger persons. This may be caused by agerelated sensitivity to the drug, or because the metabolism and excretion of the drug is slower in the older adult.
In all phases of clinical trials, the risks and benefits to susceptible populations must be evaluated. These populations include infants, young children, pregnant women, nursing mothers, and older adults.
Clinicians who are experts on the disease being treated are used as investigators during Phase I and Phase II clinical trials. In Phase III, the usefulness of the drug in an expanded patient base is evaluated and adverse effects that may not have appeared in the previous two phases may become apparent during this period. The drug may be withdrawn from testing at any time if the risk to patients outweigh the benefits.
When the drug enters Phase IV, any adverse event reported to the manufacturer must be reported to the FDA within fifteen days after initial receipt of the information. This allows for continued evaluation and, if necessary, warnings to be issued by the FDA to prescribing physicians, pharmacists, and the public. In extreme cases, it may warrant the removal of the drug from the market.
The FDA requires that postmarketing adverse drug events be reported at quarterly intervals for three years from the date of approval of the NDA, and then at annual intervals. This provides an ongoing evaluation of the benefit-to-risk ratio of new drugs. It also gives recognition to the rights of all patients who participate in clinical drug studies in all stages of development.