What is the term for the ability of a drug to enter the bloodstream from its site of administration?

The term that refers to the ability of a drug to enter the bloodstream from its site of administration is absorption. This process encompasses how quickly and efficiently a drug is taken up into the circulatory system after being administered, which can depend on various factors such as the method of administration (oral, intravenous, etc.), the drug's formulation, and the physiological characteristics of the individual.

Absorption is a critical step in pharmacokinetics, as it influences the drug's effects and overall efficacy. Factors such as the solubility of the drug and its ability to cross biological membranes play significant roles in how well it is absorbed. Following absorption, the drug can then be distributed throughout the body to reach its target tissues or organs, which is part of the subsequent stage known as distribution.

Other processes like excretion and metabolism are related but distinct. Excretion refers to the elimination of drugs from the body, often through the kidneys, while metabolism involves the chemical alteration of the drug within the body, which can sometimes affect how it is absorbed or distributed. Understanding these differences is crucial in the study of pharmacology and veterinary medicine, particularly when working with laboratory animals.