The plasma concentration of a drug that has been partially removed during dialysis can be restored to the desired level using the following equation to calculate a loading dose (LD) of the drug:
Where Cchange= desired change in plasma concentration and VD= volume of distribution
For example, to increase the plasma concentration of phenytoin by 5 mg/L (5mcg/mL), the clinician would multiply 5 mg/L by the phenytoin volume of distribution, 0.7L/kg, resulting in a loading dose of 3.5 mg/kg.
Reviewed and revised February 2004 by Steven C. Schachter, MD, epilepsy.com Editorial Board.
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