• # Calculation

Posted by on December 9, 2022 at 3:34 pm

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

• ### R.Ph. Shams

December 30, 2022 at 11:57 am

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.