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elimination phase - the period of time after a drug has reached its full volume of distribution and is being cleared from the plasma elimination rate constant (kel) - a rate constant that describes rate of elimination for a drug. Elimination rate constants normally correspond to first-order processes and have units of inverse time. endogenous ligand - a ligand that is found naturally in the body enzyme (E) - usually a protein, a biological catalyst that converts a substrate to a product enzyme-substrate complex (E-S) - the aggregate substance formed by binding between an enzyme and its substrate excretion - the removal of waste from the body. For drugs, excretion is normally associated with the generation of urine by the kidneys through the filtration of blood. exogenous ligand - a ligand that is not naturally found in the body. Synthetic drugs that bind receptors are exogenous ligands. extraction ratio - the fraction of a drug that is removed by an organ based on the plasma concentration of a drug that enters and leaves the organ F - see bioavailability false negatives - compounds that fail to appear active in a screen despite the fact that the compounds do possess strong binding to the target of interest false positives - compounds that indicate activity in a screen but are actually not active fast neurotransmitter - a neurotransmitter that acts as a ligand for a ligand-gated ion channel first pass effect - the tendency for a significant fraction of an oral drug to be broken down the liver immediately after absorption from the digestive tract

MOOC Medicinal Chemistry