What does the term 'absorption' refer to in pharmacology?

In pharmacology, 'absorption' specifically refers to the process by which a drug moves from the site of administration into the bloodstream, leading to its entry into systemic circulation. This is a critical step because only drugs that are absorbed effectively can exert their therapeutic effects throughout the body. For example, when a medication is taken orally, it must first dissolve in the gastrointestinal tract and then be absorbed through the intestinal walls into the blood before it can reach its target tissues.

Understanding absorption is essential for determining how quickly and at what concentration a drug will act in the body. Factors such as the formulation of the drug, the route of administration, and the physiological conditions of the individual's body can all impact this process, making it a key consideration in pharmacokinetics and drug development.