Pharmacology Demystified

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PHASE II: LIMITED CONTROLLED EVALUATION
The purpose of Phase II evaluation is to monitor drug effectiveness and any side
effects. Individuals with the targeted disease participate in this phase of drug
trials. For example, antihypertensive (blood pressure lowering) drugs will be
administered to patients who have hypertension (high blood pressure) to determine
the drug’s effectiveness or optimal dose response range and for side
effects. The number of participants is larger than Phase I trials but usually does
not exceed 100 persons and every effort is made to use only people who have no
other disorders or diseases.
PHASE III: EXTENDED CLINICAL EVALUATION
Phase III drug trials include many physicians and large groups of participants.
When enough information has been collected to justify continued use of the
drug, a New Drug Application (NDA) is submitted to the FDA. Usually, more
than 4 years has passed between the drug’s selection and the filing of the NDA.
Phase IV studies are also called post-marketing follow-up. They are voluntarily
conducted by pharmaceutical companies. These studies continue after the
FDA has approved the drug and often include populations such as pregnant
women, children, and the elderly. Manufacturers can find low-level side effects
or can find that a drug is toxic and must be removed from market. The FDA continues
to monitor new drugs even after they are marketed.
Drugs also undergo tests to determine the possible effects on a fetus. As a result
of these tests, drugs are classified using the following Pregnancy Categories.
Category A
Adequate and well-controlled studies indicate no risk to the fetus in the first
trimester of pregnancy or later.
Category B
Animal reproduction studies indicate no risk to the fetus, however there are no
well-controlled studies in pregnant women.
Category C
CHAPTER 1 An Inside Look at Pharmacology
Animal reproduction studies have reported adverse effects on the fetus, however
there are no well-controlled studies in humans but potential benefits may indicate
use of the drug in pregnant women despite potential risks.