Equation expressing the build up and decay in concentration of a substance (usually in plasma) based on first order uptake and elimination in a one compartment model, having the form C = [ƒDκa/V(κa - κe)][exp(-κet) - exp(-κat)] where C is the concentration and D the dose of the substance, ƒ the fraction absorbed, and V the volume of distribution. κa and κe) are the first order rate constants of uptake and elimination, respectively, and t is time.[2]
