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A loading dose is most useful for drugs that are eliminated from the body relatively slowly, i.e. have a long systemic half-life. Such drugs need only a low maintenance dose in order to keep the amount of the drug in the body at the appropriate therapeutic level, but this also means that, without an initial higher dose, it would take a long ...
The method of approach to steady state has also been used to analyze the change in messenger RNA levels when synthesis or degradation changes, and a model has also been reported in which the plateau principle is used to connect the change in messenger RNA synthesis to the expected change in protein synthesis and concentration as a function of time.
Continuing the maintenance dose for about 4 to 5 half-lives (t 1/2) of the drug will approximate the steady state level. [1] One or more doses higher than the maintenance dose can be given together at the beginning of therapy with a loading dose. [2] A loading dose is most useful for drugs that are eliminated from the body relatively slowly ...
In pharmacokinetics, steady state refers to the situation where the overall intake of a drug is fairly in dynamic equilibrium with its elimination. In practice, it is generally considered that once regular dosing of a drug is started, steady state is reached after 3 to 5 times its half-life. In steady state and in linear pharmacokinetics, AUC ...
The accumulation ratio of a specific drug in humans is determined by clinical studies.According to a 2013 analysis, such studies are typically done with 10 to 20 subjects who are given one single dose followed by a washout phase of seven days (), and then seven to 14 repeated doses to reach steady state conditions.
The steady state or stable concentration is reached when the drug's supply to the blood plasma is the same as the rate of elimination from the plasma. It is necessary to calculate this concentration in order to decide the period between doses and the amount of drug supplied with each dose in prolonged treatments.
A physiologic interpretation of clearance (at steady-state) is that clearance is a ratio of the mass generation and blood (or plasma) concentration. Its definition follows from the differential equation that describes exponential decay and is used to model kidney function and hemodialysis machine function:
Therefore the dose required to give a certain plasma concentration can be determined if the V D for that drug is known. The V D is not a real volume; it is more a reflection of how a drug will distribute throughout the body depending on several physicochemical properties, e.g. solubility, charge, size, etc.