Drug distribution , volume intravenous infusion rate

Equation 9.98 permits one to calculate the infusion rate necessary to attain and then maintain the desired steady-state plasma concentration of a drug if the systemic clearance of the drug is available. Equation 9.98 also provides a convenient way to determine the apparent volume of distribution of a drug by means of intravenous infusion experiment if the infusion rate (Q), the elimination rate constant (K), and the steady-state plasma concentration (C )gg are known. 

As shown above, early/late sampling will require the use of equations to adjust observed high and low concentrations to achieve more accurate estimates of the "peak" and trough concentrations. Early/late sampling will also have ramifications for the equations used to for solve for the apparent volume of distribution and the elimination rate constant by using two steady-state plasma drug concentrations sampled after a multiple intravenous infusion. Table 14.4 summarizes these equations. 

Therefore, it is a common practice to use values of the elimination rate constant, the elimination half life and the apparent volume of distribution obtained from intravenous bolus or infusion data to compute parameters associated with extravascular administration of a drug. 

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