What are the four main phases of pharmacokinetics?

• A. Administration, Efficacy, Distribution, Metabolism
• B. Absorption, Distribution, Metabolism, Excretion
• C. Definition, Production, Usage, Elimination
• D. Ingestion, Release, Binding, Removal

Answer: (B)

The four main phases of pharmacokinetics—absorption, distribution, metabolism, and excretion—describe how a drug travels through and is processed by the body.

Absorption refers to the process by which a drug enters the bloodstream after administration. This phase is crucial because it determines how quickly and effectively the medication will reach its target site. Factors like the route of administration (oral, intravenous, etc.), the drug’s formulation, and the presence of food can all influence this phase.

Distribution involves the dispersion of the drug throughout the body’s fluids and tissues. After it enters the bloodstream, the drug must reach its intended sites of action. This process is affected by blood flow to tissues, the ability of the drug to cross cell membranes, and binding to plasma proteins.

Metabolism is the biochemical modification of the drug, primarily occurring in the liver. The body chemically alters the drug to facilitate its elimination. This phase is essential for converting lipid-soluble compounds into water-soluble metabolites that can be more readily excreted.

Excretion is the final phase, where the drug and its metabolites are eliminated from the body, typically through the kidneys in urine or through bile into feces. Efficient excretion is crucial for maintaining therapeutic levels of medication