Simulated Effect of Gentamicin Assay Errors on Calculated Pharmacokinetic Values
The effects of errors in gentamicin concentrations were assessed using computer simulation. Steady-state concentrations at the end of a one-hour infusion (Cmax) and at the end of the dosing interval (Cmin) were calculated for four simulated patients with three dosing schemes each. Errors from -80% to +80% were systematically induced in Cmax or Cmin, or both. Pharmacokinetic values were calculated from the error concentrations and then used to determine new dosing regimens given specific desired concentrations. True Cmax and Cmin values were calculated using the new dosing regimens and original pharmacokinetic values. As the absolute value of the induced error increased, increases were generally seen in the absolute value of the resultant error and in the deviation of the true Cmax and Cmin from desired values. Resultant error was more evident with induced error less than zero, when error was induced into Cmax, and with shorter dosing intervals. Resultant error in pharmacokinetic variables was greater than induced error at induced errors as low as +/- 5%. Toxic and suboptimal values for the true Cmax and Cmin rarely occurred with induced errors of -20% to +20%. Errors in serum gentamicin concentration measurements are more likely to cause larger resultant errors as the errors in concentration values (1) increase in magnitude, (2) result in underreporting of the concentration values, or (3) affect peak concentration values. Shorter dosing intervals may also increase the influence of assay errors.
Boyce, E. G.,
Pugh, C. B.
Simulated Effect of Gentamicin Assay Errors on Calculated Pharmacokinetic Values.
Clinical Pharmacy, 7(4), 307–313.