What is the term for the speed at which a drug enters the bloodstream?

The term that describes the speed at which a drug enters the bloodstream is referred to as the absorption rate. This process involves the movement of a drug from its site of administration into the systemic circulation, where it becomes available for therapeutic action. Various factors can influence the absorption rate, including the route of administration (oral, intravenous, intramuscular, etc.), the drug's formulation, its solubility, and the presence of food in the gastrointestinal tract. Understanding the absorption rate is crucial for determining the onset of action of a medication and its overall effectiveness in achieving the desired therapeutic outcomes.

Metabolism, on the other hand, refers to the body's process of breaking down and converting drugs into different chemical forms, primarily in the liver. The distribution rate pertains to how quickly a drug disperses throughout the body once it enters the bloodstream. Elimination rate is the speed at which the drug is removed from the body, primarily through urine or feces. Each of these terms relates to different stages of a drug's pharmacokinetic journey, but only the absorption rate specifically addresses the initial entry of a drug into the bloodstream.