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Absolute bioavailability refers to the bioavailability of a drug when administered via an extravascular dosage form (i.e. oral tablet, suppository, subcutaneous, etc.) compared with the bioavailability of the same drug administered intravenously (IV). This is done by comparing the AUC of the non-intravenous dosage form with the AUC for the drug ...
To ensure that the drug taker who has poor absorption is dosed appropriately, the bottom value of the deviation range is employed to represent real bioavailability and to calculate the drug dose needed for the drug taker to achieve systemic concentrations similar to the intravenous formulation. [4]
In pharmacokinetics, the rate of infusion (or dosing rate) refers not just to the rate at which a drug is administered, but the desired rate at which a drug should be administered to achieve a steady state of a fixed dose which has been demonstrated to be therapeutically effective. Abbreviations include K in, [1] K 0, [2] or R 0.
A V D greater than the total volume of body water (approximately 42 liters in humans [5]) is possible, and would indicate that the drug is highly distributed into tissue. In other words, the volume of distribution is smaller in the drug staying in the plasma than that of a drug that is widely distributed in tissues. [6]
There are various competing calculation methods for the drug accumulation ratio, yielding somewhat different results. A commonly used formula defines R ac as the ratio of the area under the curve (AUC) during a single dosing interval under steady state conditions to the AUC during a dosing interval after one single dose: [1]
At a practical level, a drug's bioavailability can be defined as the proportion of the drug that reaches the systemic circulation. From this perspective the intravenous administration of a drug provides the greatest possible bioavailability, and this method is considered to yield a bioavailability of 1 (or 100%). Bioavailability of other ...
In first-order (linear) kinetics, the plasma concentration of a drug at a given time t after single dose administration via IV bolus injection is given by; = / where: C 0 is the initial concentration (at t=0)
In pharmacokinetics, a loading dose is an initial higher dose of a drug that may be given at the beginning of a course of treatment before dropping down to a lower maintenance dose. [ 1 ] A loading dose is most useful for drugs that are eliminated from the body relatively slowly, i.e. have a long systemic half-life .