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Pharmacology is the study of how drugs (chemicals) affect the physiology of the body. Physical therapists and physical therapist assistants have direct contact with patients taking medication to impact response to exercise and movement. Most of your patients will be taking medication related to their condition, and it is important to understand how drugs will impact the patient and physical therapy treatment. Patients today have access to prescribed medications and over-the-counter (OTC) formulations such as herbs, vitamins, and tinctures. The benefits of both OTC and prescribed medications are varied, but a key point is a need for health care professionals to understand the benefits, side effects, signs, and symptoms of medications working correctly or when they are not. This section will provide a general overview of the basic principles of pharmacology.

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Agonist A compound that binds to a receptor and produces a biological response.
Antagonist Blocks or reverses the effect of an agonist—they have no effect on their own.
Absorption A process involving the movement of a substance from its side of administration across one or more body membranes. A drug may be absorbed locally or produce a biological effect at a distant site.
Bioavailability Refers to how completely the system absorbs a particular drug and is available to produce a response.
Distribution The process by which drugs are transported after they have been absorbed or administered directly into the bloodstream.
Excretion The process by which drugs are removed from the body through urine, exhalation, sweat, saliva, bile, feces, and tears.
Efficacy The maximal response a drug can produce.
First-pass effect The liver is a metabolic machine and often inactivates drugs on their way from the GI tract to the body, called the first-pass effect.
Metabolism The process where the drugs are made less or more active.
Partial agonist Produces the biological response but cannot produce 100% of the biological response even at very high doses.
Pharmacokinetics The effects of the body on drugs are related to four processes: absorption, distribution, metabolism, and excretion.
Pharmacodynamics The drug’s action on the body, such as the mechanism of action or how the drug exerts its effects.
Potency A measure of the dose that is required to produce a response.
Receptor A specialized target macromolecule that binds a drug and mediates its pharmacologic action.
Topical drug A topical drug is applied locally to the skin and membranous linings of the eyes, ears, nose, respiratory tract, urinary tract, vagina, and rectum.
Volume distribution The volume of plasma, or fluid, in which the drug is dissolved, indicates the extent of distribution of that drug.

Drugs are commonly organized in two major ways by their therapeutic effect and pharmacologic classification. The therapeutic effect classifies a medication by its clinical action using biochemical and physiologic principles—“a drug used for high blood pressure,” “a drug used for pain.” Pharmacologic classification addresses how ...

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