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
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 ...