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Experimental study designs are the primary method for testing
the effectiveness of new therapies and other interventions, including
innovative drugs. By the 1930s, the pharmaceutical industry had
adopted experimental methods and other research designs to develop
and screen new compounds, improve production outputs, and test drugs
for therapeutic benefits. The full potential of experimental methods
in drug research was realized in the 1940s and 1950s with the growth
in scientific knowledge and industrial technology.1
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In the 1960s, the controlled clinical trial, in which a group
of patients receiving an experimental drug is compared with another
group receiving a control drug or no treatment, became the standard
for doing pharmaceutical research and measuring the therapeutic
benefits of new drugs.1 By the same time, the double-blind
strategy of drug testing, in which both the patients and the researcher
are unaware of which treatment is being taken by whom, had been
adopted to limit the effect of external influences on the true pharmacological
action of the drug. The drug regulations of the 1960s also reinforced
the importance of controlled clinical trials by requiring that proof
of effectiveness for new drugs be made through use of these research
methods.2,3
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In pharmacoepidemiology, the primary use of experimental design
is in performing clinical trials, most notably randomized, controlled
clinical trials.4 These studies involve people as the units
of analysis. A variation on this experimental design is the community
intervention study, in which groups of people, such as whole communities,
are the unit of analysis. Key aspects of the clinical and community
intervention trial designs are randomization, blinding, intention-to-treat
analysis, and sample size determination.
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An experiment is a study designed
to compare benefits of an intervention with standard treatments,
or no treatment, such as a new drug therapy or prevention program,
or to show cause and effect (see Figure 3-2). This type of study
is performed prospectively. Subjects are selected from a study population, assigned
to the various study groups, and monitored over time to determine
the outcomes that occur and are produced by the new drug therapy,
treatment, or intervention.
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Experimental designs have numerous advantages compared with other
epidemiological methods. Randomization, when used, tends to balance
confounding variables across the various study groups, especially
variables that might be associated with changes in the disease state
or the outcome of the intervention under study. Detailed information
and data are collected at the beginning of an experimental study
to develop a baseline; this same type of information also is collected
at specified follow-up periods throughout the study. The investigators
have control over variables such as the dose or degree of intervention.
The blinding process reduces distortion in assessment. And, of great
value, and not possible with other methods, is the testing of hypotheses.
Most important, this design is the only real test of cause–effect
relationships.
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The disadvantages of experimental design involve subject participation
criteria ...