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Post-marketing surveillance (PMS) is the identification and collection of information regarding medications after their approval by the U.S. Food and Drug Administration (FDA). Systematic PMS of drugs began in the early 1970s and has increased substantially since then. The monitoring of drugs after their approval has become necessary for many reasons. In the 1950s and 1960s, there were fewer drugs available and, thus, fewer drugs to monitor. Today, drugs are being developed and consumed at increasingly high rates. Other factors contributing to the need for PMS include changes in the FDA’s approval process. As discussed in Chapter 4, this lengthy process has been criticized. The FDA has responded by developing channels and opportunities for patients in need to obtain critical drugs. As a result, the dangers associated with use of some drugs may not be determined in the premarketing phase.


PMS is conducted by various types of organizations and agencies, including pharmaceutical manufacturers, universities, government agencies, private companies, and consumer advocacy groups. The purpose of conducting PMS may differ, depending on the perspective of the individuals conducting the surveillance. This chapter provides an overview of PMS, including its definition and purpose, available methods, and several examples of the application of PMS in clinical practice.


Since the drug approval process involves phase I, II, and III trials, post-marketing trials are sometimes referred to as phase IV trials. PMS involves systematic monitoring of medications as they are used in real-life scenarios, as opposed to the controlled settings of pre-marketing trials, where study conditions are tightly controlled. Although randomized, RT clinical trials, which minimize variability, are useful in assessing the efficacy of one drug versus another, they do not provide adequate information on a drug’s effects after it is released for general use.


PMS provides valuable information on the use of drugs in special patient populations, which is information not easily obtainable from pre-marketing studies. Randomized clinical trials conducted before marketing include only subjects who meet defined inclusion and exclusion criteria, thus creating a homogenous study population. The population of potential users after the drug is released is very different from the population studied in the pre-marketing phase. For example, randomized clinical trials typically exclude from study participation women who are pregnant or breastfeeding; therefore, PMS is the only means of obtaining information on mutagenic and teratogenic effects of drugs in humans. Other special populations that benefit from PMS include the elderly and patients with multiple comorbidities. Like pregnant women, patients who are very old or very sick are excluded from premarketing trials. A drug may exhibit different effects when administered to a healthy 30-year-old patient versus an 85-year-old patient who has multiple health problems and is taking multiple medications.


PMS also allows for long-term monitoring of the effects of drugs. Due to cost and feasibility issues, randomized clinical trials conducted before marketing are short in duration. Thus, experience with drugs at the time ...

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