Drug Clearance

Question 0

Steady state drug concentration

Answer 0

Non IV dose and absorption takes a while and starts to build up
As you build up more and more, elimination reaches the same level as the amount added, elimination takes over
Add maintenance doses to make up for the elimination and keep a steady state

Question 1

Clearance

Answer 1

Relates the plasma concentration to the elimination rate
P = C, mg/ml in plasma
P (Cl) = UV
U=urine concentration of drug (mg/ml)
V=rate of urine production (ml/min)
Clearance is the ml of plasma that can be completely cleared of drug each minute, ml/min
UV=mg/ml eliminated

Question 2

Glomeruli

Answer 2

Filtration unit in the kidney
Polar form can be secreted into the tubule
Can also reabsorb nonpolar form of the drug into the blood stream

Question 3

Glomerular filtration rate

Answer 3

GFR

volume of plasma water filtered by the kidney each minute

Question 4

Inulin

Answer 4

Ideal substance for measurement of GFR
Freely filtered at the glomeruls, not secreted or reabsorbed
Insulin clearance is the volume of plasma cleared of insulin each minute
About 130ml/min for a 70kg ma

Question 5

Drug and inulin clearance

Answer 5

If clearance of the drug is greater than the clearance of inulin–net secretion in tubule

If clearance of the drug is less than the clearance of inulin–net reabsorption into plasma

Question 6

Half-life

Answer 6

kr = Cl_r / Vd
First order rate equation, rate of elimination
Half life is the amount of time it takes half of the remaining drug to be eliminated
t1/2 = ln2 / kr
t1/2 = 0.693 / kr
t1/2 = 0.693 Vd / Cl_r