What is the first step that occurs in pharmacokinetics?

In pharmacokinetics, the first step that occurs is absorption. Absorption refers to the process by which a drug is taken into the bloodstream from its site of administration. This is crucial because before a drug can exert its intended effects on the body, it must first be absorbed into the systemic circulation. The method of administration, such as oral, intravenous, or intramuscular, can significantly influence the rate and extent of absorption.

Once absorption occurs, the drug can then be distributed throughout the body (the next step in pharmacokinetics), metabolized, and eventually excreted. Each of these steps plays a role in determining the overall pharmacological effect of the drug. Understanding absorption is essential for evaluating how quickly a drug will act and how much of it will ultimately be available to exert its therapeutic effects.