Pharmacokinetics Flashcards
How do drug conc decline?
In a non linear fashion
Pharmacokinetics
How body deals with drug
Absorption, distribution, metabolism, excretion
Half life
Time it takes for drug conc to drop by half
Tells you how drug behaves
What is the Cp power 0?
Conc at 0 time
How many half life’s till drug gets to 3.13% (essentially left the body)?
5 half lives
Half life of ameomerone= 45days. How long does it take to leave the body?
8 months (ish)
Ideal half life?
24hrs
Half life of warfarin? Why is this good?
36hrs. Can be taken once a day, more patient compliance.
Define ‘1st order process’
Half life & rate of decline is dependant on concentration of drug
Volume distribution=
Dose ✖️ Cp0
Clearance of drug=
Dose ➗ area under curve
What is the area under the curve at low clearance?
Area under curve is high
Why does ameomerone have a long half life?
Vol of distribution is very high
Slope of line=
Elimination rate constant (kel)
Kel=
Elimination rate constant (slope of line)
Blood clearance =
Vol of blood cleared of drug in unit time
Cl= Vd ✖️ kel (slope of line)
Sum of metabolic & renal Cl
Area under curve
CL=
Dose ➗ area under curve
Vd ✖️ kel
What happens to area under curve if dose doubles?
It doubles
What happens to AUC if clearance is halved?
It doubles
Kinetics of accumulation is the same as kinetics of ………..
Elimination
How many half life’s till a drug reaches a steady state?
5 (same as elimination!)
What predominates in phase 1?
Distribution
What predominates in phase 2?
Elimination
Half life of heparin?
- 5hrs
7. 5 hrs to disappear
T 1/2 (half life) =
- 693 ➗ kel
0. 693 is natural log of 2 so use to find half life
Cp (ss) = conc at a steady state =
Infusion rate ➗ Cl
Bioavailability✖️dose) ➗ (CI✖️dosing interval
What do you do to infusion rate in patients with heart failure?
Decrease it
What does Cp (ss) stand for?
Conc at a steady state
Km=
1/2 Vmax
