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The aim of drug dosing is to maintain pharmacokinetics (a similar peak, trough, or average steady-state drug concentration) to achieve a desired pharmacodynamic response without adverse side effects.1 In critically ill patients receiving renal replacement therapy (RRT), however, determining appropriate drug dosing is challenging because pharmacodynamic target attainment is determined by a complex interplay between drug dosing, pharmacokinetic changes within the critically ill patient, and the type of RRT selected (Table 112–1).2 A stepwise approach for patients with chronic kidney disease and acute kidney injury has been proposed (Table 112–2).3 For assessment of kidney function, estimation by equation is generally more accurate than measured creatinine clearance, given errors in urine collection.4 Therefore, the National Kidney Disease Education Program in the United States recommends estimation of the glomerular filtration rate from the Cockcroft and Gault equation for adults: urinary creatinine clearance = (140 – age [years]) × weight (kg) × 0.85 (for female)/serum creatinine (mg/dL) × 72 or the Schwartz equation for children.5,6
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