Unit 1: Pharmacokinetics

Question 1

Pharmacokinetics

Answer 1

What the body does with the drug

Question 2

Goal of pharmacotherapy

Answer 2

Attain therapeutic effect with minimal toxicity/adverse event

Question 3

Pharmacokinetics vs pharmacodynamics

Answer 3

What the body does with the drug
vs
From a given concentration, what clinical response might we see?

Question 4

Clearance

Answer 4

Measure of ability of body to eliminate drug

Question 5

Volume of distribution

Answer 5

Measure of apparent space in body available to contain drug

i.e. where the drug goes when it is put into the body

Question 6

Formula for volume of distribution, V

Answer 6

V=(amount of drug in body)/C

C: concentration of drug in blood or plasma

Question 7

Formula for clearance, CL

Answer 7

CL = (rate of elimination) / C

C: drug concentration

Question 8

2 major elimination sites

Answer 8

Kidneys

Liver

Question 9

Renal clearance is ______ ?

Answer 9

Unchanged drug in urine

Question 10

Liver clearance happens how?

Answer 10

1. Unchanged drug secreted via bile and the large intestine

2. Biotransformation of drug into 1+ metabolites

Question 11

Formula for

Rate of elimination = ?

Answer 11

Rate of elimination = CL x C

Clearance x Concentration

i.e. the area under the curve

Question 12

FLOW DEPENDENT ELIMINATION
aka ________________

definition: _____________

Answer 12

FLOW DEPENDENT ELIMINATION
aka “first order kinetics” or “first order elimination”

definition: drugs are cleared dependent on blood flow through organ

Question 13

CAPACITY-LIMITED ELIMINATION
aka ________________

definition: ________________

Answer 13

CAPACITY-LIMITED ELIMINATION
aka “zero order kinetics”

definition: rate of clearance varies depending on concentration of drug achieved (e.g. alcohol) due to pathways becoming saturated

Question 14

Half life

Answer 14

Amount of time needed to cut amount of drug in half

Question 15

Steady state is usually attained after ______ half lives

Answer 15

4

Question 16

Bioavailability

Answer 16

Fraction of unchanged drug reaching systemic circulation following administration by any route

Question 17

Acidic drugs are better absorbed in ______

Answer 17

Acidic environments like the stomach and small intestines

Question 18

Alkalotic drugs are uncharged and better absorbed in _______

Answer 18

The small intestine (which is often neutral but sometimes alkalotic)

Question 19

Maintenance dose

Answer 19

Dose required to reach steady state

Question 20

Loading dose: why do we give this?

Answer 20

Half life of drug is so long that it would take days to reach steady state; a loading dose promptly raises concentration in plasma to target

Question 21

Highly protein bound drugs: readily absorbed or not?

Answer 21

Tend to stay in vasculature

Question 22

Physiologic Variables affecting Pharmacokinetics

Answer 22

— albumin, if drugs are protein bound
— Input: is the patient taking the medication consistently?
— Clearance: abnormalities occur with heart, liver, and kidney failure
— Volume of Distribution: Vd - balance in binding to tissues (decreases plasma volume) and binding to plasma (increases plasma volume)
— Half-life: half life may increase with age but without changes in clearance

Question 23

The more common kind of elimination

Answer 23

Flow Dependent Elimination

FIRST ORDER ELIMINATION

FIRST ORDER KINETICS

Question 24

Define: Elimination Constant

Answer 24

amount removed per unit of time