# Pharmacokinetics-PHAR2102

### Description

practice calculations for phar2101
Flashcards by jenny schneider, updated more than 1 year ago
 Created by jenny schneider about 9 years ago
140
1

## Resource summary

 Question Answer What IV bolus loading dose would be required if you need to achieve 2mg/L and Vd is 50L? LD=CssVd so need 2 x 50 = 100mg You are commencing an IV infusion to achieve Css=4mg/L. The clearance of the drug is 10L/h, what would be the required infusion rate? Css=ko/CL so ko= 4mg/L x 10L/h=40mg/h If you commence an infusion at 40mg/h and the half-life of the drug is 4h, how long until steady-state plasma drug concentration is achieved? it takes about 5 half-lives to reach steady state therefore about 20h The plasma drug concentration of a drug after an IV bolus is 10ng/mL 4h after dosing and it is 5ng/mL 8h after dosing. What is k? what is elimination half-life? Cp2=Cp1e^-kt k= 0.174h-1 t/12= 4h If Vd=50L and k=0.1h-1, what is CL? CL=kVd CL=50 x 0.1= 5L/h If we administer an IV bolus dose of 500mg and collect urine so we collect all drug that is excreted unchanged and the amount collected = 300mg, what is the fraction excreted unchanged? fe= amount in urine/dose reaching systemic circulation= 300/500=0.6 if we administer an oral dose of 500mg and F=0.8 and we collect all urine so that we determine that 100mg is excreted unchanged, what is fraction excreted unchanged (fe)? 100/(0.8 x 500)=0.25 A patient is receiving 250mcg digoxin daily and the bioavailability of tablet is 0.7. At steady-state the Cssav= 1ng/mL, what is the clearance of the drug in this patient? 1ng/mL=1mcg/L (matching units!!) Cssav= (FxDose)/(CL.T) 1mcg/L=(0.7 x 250mcg)/CL x 24h CL=7.3L/h If patient is receiving 125mcg digoxin tablets orally daily and F=0.7 and CL=2L/h, what would be the Cssav achieved? Cssav=FD/CL.T =(0.7 x 125)/2 x 24 Cssav=1.8mcg/L=1.8ng/mL If a patient is taking a 250mcg Digoxin tablet daily which has oral bioavailability of 0.6 and is now to be swapped to digoxin elixir (50mcg/mL) which has a bioavailability of 0.8, how many mL of digoxin elixir would be the appropriate dose? 250mcg x0.6=150mcg reaching systemic circulation from tablet 150mcg/0.8=187.5mcg as elixir 187.5/50=3.75mL

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