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The elimination rate constant K or K e is a value used in pharmacokinetics to describe the rate at which a drug is removed from the human system. [1] It is often abbreviated K or K e. It is equivalent to the fraction of a substance that is removed per unit time measured at any particular instant and has units of T −1.
Clearance of a substance is sometimes expressed as the inverse of the time constant that describes its removal rate from the body divided by its volume of distribution (or total body water). In steady-state, it is defined as the mass generation rate of a substance (which equals the mass removal rate) divided by its concentration in the blood.
The rate constants kepr and kb describe extravasation from circulation into the tumor, and intravasation back into the circulation, respectively. The rate constant kel represents clearance by the kidneys, MPS, and any other non-tumor elimination processes, such that when kb = 0, k10 = kepr + kel where kel is the elimination rate constant.
The most important inference derived from the steady state equation and the equation for fractional change over time is that the elimination rate constant (k e) or the sum of rate constants that apply in a model determine the time course for change in mass when a system is perturbed (either by changing the rate of inflow or production, or by ...
For example, the concentration in other areas may be approximately related by known, constant factors to the blood plasma concentration. In this one-compartment model, the most common model of elimination is first order kinetics , where the elimination of the drug is directly proportional to the drug's concentration in the organism.
where k is the reaction rate constant. Such a decay rate arises from a first-order reaction where the rate of elimination is proportional to the amount of the substance: [ 39 ] d C d t = − k C . {\displaystyle {\frac {dC}{dt}}=-kC.}
Gross profit grew by 10.3% at constant exchange rate to 31.1 billion with a gross margin of 75.7%. ... the entire elimination of all factoring of receivables for 1.4 billion euros; and third, an ...
The other elimination pathways are less important in the elimination of drugs, except in very specific cases, such as the respiratory tract for alcohol or anaesthetic gases. The case of mother's milk is of special importance. The liver and kidneys of newly born infants are relatively undeveloped and they are highly sensitive to a drug's toxic ...