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## 1 Medications ### Drug * A drug is a substance used to diagnose, treat, cure, prevent, or mitigate disease in humans or animals. ### Pharmacology * Pharmacology is defined as the scientific study of the action of drugs on a living system, with receptors and produces a biological response. #...

## 1 Medications ### Drug * A drug is a substance used to diagnose, treat, cure, prevent, or mitigate disease in humans or animals. ### Pharmacology * Pharmacology is defined as the scientific study of the action of drugs on a living system, with receptors and produces a biological response. ### Pharmacokinetics * Pharmacokinetics involves the absorption, distribution, metabolism, and elimination (excretion) of a drug in a living system. * Absorption is the manner by which drug molecules travel from the site of administration across cell membranes to the site of action. Absorption is affected by pH, blood flow, body surface area, contact time at the absorption surface, and tissue thickness. * Distribution is the means by which the drug travels from the circulatory system across barrier site of action (Fig. 1.1). Drug distribution is affected by the drug’s properties, protein binding, and anatomical barriers. A drug’s metabolism is affected by nutritional status, and gender. * Metabolism is the process involving the conversion of active drugs to a compound that can easily be removed or the conversion of prodrugs to active drugs. * Elimination (excretion) is the process by which a drug is removed from the body. Drugs are eliminated by the kidney, lung, and include disease states, a drug’s ionization, drug interactions, and a drug’s half-life. ### Bioavailability * The rate and extent to which the active ingredient or active entity is absorbed from a drug product and becomes available at its site of action. ### Bioequivalence * The rate and extent of absorption of an active ingredient from a drug product so that it becomes available at its site of action. ### Narrow Therapeutic Index * Narrow therapeutic index (NTI) drugs are defined as those drugs for which small differences in dose or blood concentration may lead to therapeutic failures or adverse reactions. Serious adverse reactions are those that are persistent, possibly irreversible, or life-threatening, hospitalization, disability, or even death. * Characteristics of NTI drugs: * Steep drug dose-relationship within the usual dose range or narrow span between effective **Image Description:** Below the text is a diagram illustrating drug distribution and its effects on different organs and tissues: * Central section: A capsule labeled "Drug" is shown, with arrows indicating the direction of drug movement. * Organs: Arrows lead to the brain, heart, and kidney. The brain and heart are associated with high blood flow and rapid distribution, while the kidney is associated with rapid distribution. The text labels each organ and indicates the direction of the blood flow. * Tissues: Skeletal Muscle, Adipose tissue, and Skin. The skeletal muscle has a slow distribution and low blood flow is marked with arrows. Adipose tissue is shown to have drug distribution. The skin has the text "low blood flow" with the text "slow distribution" with arrows. * Labels: The diagram is labeled "Fig. 1.1 Distribution. (From Raffa RB, Rawls SM, Beyzavi EP. Netter’s. Illustrated pharmacology, Philadelphia, 2005, Saunders.)