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Pharmacology is the study of drugs. In its broadest definition, a drug can be described as “any substance that, when taken into a living organism, may modify one or more of its functions.”1 In this sense, a drug includes any substance that alters physiological function in the organism, which may have positive or negative effects. In terms of clinical pharmacology, it has traditionally been the beneficial or therapeutic effects that have been of special interest.

For centuries, people have used naturally occurring chemicals to relieve pain or treat disease. Almost everyone, for example, has been administered some form of natural product or home remedy that was handed down from generation to generation when trying to resolve a minor illness or painful condition. However, these natural cures and home remedies are understandably limited in how well they can treat more serious conditions. Within the past 100 years, medical practitioners have therefore expanded their use of natural, semisynthetic, and synthetic chemical agents to the point where many diseases can be prevented or cured, and the general health and well-being of many individuals has dramatically improved through therapeutic drug use. Current prescribers are expected to know the drugs and the basic mechanisms of their actions. It has been long recognized that all health care professionals should have a fundamental knowledge of pharmacology as well.


As a physical therapist, occupational therapist, or other rehabilitation specialist, you can expect that your patient will be using therapeutic medications. When you know how the various drugs may affect a patient and the mechanisms behind those effects, you can apply that knowledge to determine the most appropriate interventions to achieve optimal outcomes. For instance, you can improve a patient’s therapy session dramatically by scheduling the therapy when certain drugs reach their peak effect, such as drugs that decrease pain (analgesics) or improve the patient’s motor skills (anti-Parkinson drugs). Conversely, some therapy sessions that require the patient’s active participation can be rendered useless if scheduled when medications such as sedatives reach their peak effect. Also, when you understand a drug’s pharmacological aspects, you can avoid or control any adverse responses from occurring due to direct interaction between the therapy treatment and certain medications. For example, a patient who is taking a peripheral vasodilator may experience a profound decrease in blood pressure in a hot whirlpool. By understanding the implications of such an interaction, you can be especially alert for any detrimental effects on the patient, or you may institute a different therapy treatment for them.

Pharmacology is a broad topic, so it is often subdivided into several areas of interest to help describe the discipline (Fig. 1-1). Pharmacotherapeutics is the area of pharmacology that refers to the use of specific drugs to prevent, treat, or diagnose a disease. This text’s primary concern is of the effects of drugs ...

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