Definition and scope of pharmacokinetics

 Pharmacokinetics is a branch of pharmacology that deals with the study of the movement of drugs within the body. It encompasses the processes of drug absorption, distribution, metabolism, and excretion (often abbreviated as ADME). Understanding pharmacokinetics is crucial in determining the proper dosage regimens of drugs, predicting their effects, and minimizing potential side effects or toxicity.

  1. Definition: Pharmacokinetics can be defined as the study of how the body affects a drug after administration, including the processes of absorption, distribution, metabolism, and excretion.

  2. Scope:

    a. Absorption: Absorption refers to the process by which a drug enters the bloodstream from its site of administration (e.g., orally, intravenously, topically). Factors affecting absorption include the route of administration, drug formulation, gastrointestinal motility, and the physicochemical properties of the drug molecule.

    b. Distribution: Distribution involves the transportation of drugs throughout the body via the bloodstream to their target sites of action or to various tissues and organs. Factors influencing drug distribution include blood flow, tissue permeability, plasma protein binding, and the drug's lipid solubility.

    c. Metabolism (Biotransformation): Metabolism refers to the chemical alterations that drugs undergo in the body, primarily in the liver, to convert them into more water-soluble compounds that can be excreted. The liver enzymes responsible for drug metabolism are collectively known as cytochrome P450 enzymes. Metabolism can either activate, deactivate, or convert drugs into metabolites with different pharmacological activities.

    d. Excretion: Excretion involves the removal of drugs and their metabolites from the body, primarily through the kidneys (via urine), but also through bile (via feces), lungs (via exhaled air), and sweat. Factors influencing drug excretion include renal function, urine pH, and drug reabsorption in the renal tubules.

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