What are the four main phases of pharmacokinetics?

The four main phases of pharmacokinetics are absorption, distribution, metabolism, and excretion. This sequence accurately describes how a drug moves through the body.

1. Absorption refers to how a drug enters the bloodstream after administration. This phase is critical because it influences how quickly and efficiently the drug can begin to exert its effects.

2. Distribution involves the dispersion of the drug throughout the body’s fluids and tissues. Factors such as blood flow, the ability of the drug to cross cell membranes, and its binding to plasma proteins play significant roles in this phase.

3. Metabolism is the body's process of transforming the drug into different chemical forms, primarily through liver enzymes. This process can activate, deactivate, or create metabolites that may have different effects on the body.

4. Excretion is the final phase, where the metabolites and any unchanged drug are eliminated from the body, primarily through the kidneys and urine, but also through bile, sweat, or saliva.

This comprehensive understanding of each phase highlights how drugs are processed and their therapeutic effectiveness, which is essential for optimizing drug therapy and minimizing adverse effects.