<unk>  (also known as elimination<unk> -life, pharmacologic<unk> -life) of a<unk>  substance such as medication is the time it takes from its maximum concentration (Cmax) to<unk>  of its maximum concentration in the blood plasma, and is denoted by the abbreviation '. This is used to measure the removal of things such as metabolites, drugs, and signalling molecules from the body. Typically, the<unk>  refers to the body's natural cleansing through the function of the liver and through the excretion of the measured substance through the kidneys and intestines. This concept is used when the rate of removal is roughly exponential. In a medical context,<unk> -life explicitly describes the time it takes for the blood plasma concentration of a substance to halve (plasma<unk> -life) its steady-state when circulating in the full blood of an organism. This measurement is useful in medicine, pharmacology and pharmacokinetics because it helps determine how much of a drug needs to be taken and how frequently it needs to be taken if a certain average amount is needed constantly. By contrast, the stability of a substance in plasma is described as plasma stability. This is essential to ensure accurate analysis of drugs in plasma and for drug discovery. The relationship between the<unk>  and plasma<unk> -lives of a substance can be complex depending on the substance in question, due to factors including accumulation in tissues (protein binding), active metabolites, and receptor interactions.
Biological half-life
Blood–gas partition coefficient
Rate of infusion
Peak-to-trough ratio
Minimum alveolar concentration
Toxic capacity
Dose area product
Effective dose 