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Calculation
Good evening,if any one knows which equation should I use here
1) A drug is given at the dose of 1g IV Q12H to a patient. The desired therapeutic level of the drug in the blood is 15 – 20 mg/L. When blood drawn just before the next dose, the concentration was found 10.57 mg/L. What is the appropriate dose of the drug so that the desired therapeutic level is maintained?
a) 1250 mg IV Q12H
*b) 1500 mg IV Q12H*
c) 1750 mg IV Q12H
d) 2500 mg IV Q12H
e) 1125 mg IV Q12H
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1 Reply
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At first, let’s analyze the question: R0=1g | T=12h | Ctrough (desired)=15mg/L | Cpeak (desired)=20mg/L | Ctrough=10.57mg/L.
Think outside the formulas because you don’t have time in the exam:
1000mg → 10.57mg/L (focus on units)
? → 15mg/L? = 1,419mg/L, so the answer is B.
We can’t use a formula here because we need at least Cpeak to calculate Vd and K; remember that exam questions will not ask you to do more than two steps.
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