Sawchuk-Zaske method for determining aminoglycoside dosing regimens
This method assumes that aminoglycosides are administered by intermittent iv infusion and that they follow one-compartment pharmacokinetic model.
Although aminoglycosides have been shown to follow multi-compartment pharmacokinetic model, the use of one-compartment model generally provides clinically useful estimates for drug disposition.
a- If the patient is going to receive the first aminoglycoside dose:
After administration of the first dose, three plasma samples are obtained over a period of time equivalent to the estimated .
t '
t 1/2
slope = -k/2.303
For example if the estimated is 3.5 hr, an appropriate sampling schedule can be 0.5, 1.5, and 4 hr after the end of drug administration.
i- The can be determined graphically
Or the elimination rate constant can be determined from the .
ii- The line that goes through the samples is back extrapolated to determine the plasma conc at the end of drug administration.
iii- The can be determined from the expression that describes the plasma conc at the end of drug administration because all the other parameters are known.
