Pharmacokinetics and dynamics

Question 1

Michaelis-Menten Kinetics

Answer 1

Velocity on Y-axis, [S] on X-axis

Km, Vmax are found on this

Question 2

Km

Answer 2

inversely related to the affinity of the enzyme for the substrate

Question 3

Vmax

Answer 3

directly proportional to the enzyme concentration

half of Vmax is how you find Km on the X-axis

Question 4

Lineweaver-Burk Plot

Answer 4

Plotted line crossed the Y-axis
1/V on Y axis; 1/[S] on X-axis
1/(Vmax) is when plotted line touches Y-axis
1/-Km on X-axis

Question 5

Pharmacokinetics

Answer 5

The effects of the body on the drug

Absorption, Distribution, Metabolism, Excretion

Question 6

Pharmacodynamics

Answer 6

The effects of the drug on the body

includes concepts of receptor binding, drug efficacy, drug potency and toxicity

Question 7

Bioavailability (F)

Answer 7

Fraction of administered drug that reaches systemic circulation unchanged

Question 8

Bioavailability for IV dose

Answer 8

F = 100%

Question 9

Volume of Distribution (Vd)

Answer 9

(amt drug in body)/([plasma drug])

Question 10

Vd for large/charged molecules; plasma protein bound

Answer 10

Low Vd, in blood compartment

Question 11

Vd for small hydrophilic molecules

Answer 11

Medium Vd, in ECF

Question 12

Vd for small lipophilic molecules, esp if bound to tissue protein

Answer 12

High Vd, in all tissues including fat

Question 13

Half lives to reach steady state

Answer 13

need 4-5 t1/2

Question 14

Eqtn for T1/2

Answer 14

(0.639*Vd)/(CL)

Question 15

Clearance

Answer 15

CL = (rate of elimination of drug)/([plasma drug])

Question 16

Zero Order Elimination

Answer 16

Plasma concentratino decreases linearly with time
Constant amount of drug eliminated per unit time
Phenytoin, Ethanol, Aspirin

Question 17

First Order Elimination

Answer 17

Rate of elimination is directly proportional to drug concentration

Question 18

Weak Acid Drugs

Answer 18

Phenobarbital, Methotrexate, Aspirin

Trap in basic environments so tx overdose with bicarbonate

Question 19

Weak Base Drugs

Answer 19

Amphetamines

Trap in acidic environments so tx overdose with ammonium chloride

Question 20

Phase I drug metabolism

Answer 20

Reduction, Oxidation, Hydrolysis with cyto P450

Geriatrics lose phase I first

Question 21

Phase II drug metabolism

Answer 21

Conjugation (Glucuronidation, Acetylation, Sulfation)

yields very polar, inactive metabolites

Question 22

Slow acetylators

Answer 22

Great S/E from drugs because decreased rate of metabolism

Question 23

Efficacy

Answer 23

Maximal Effect a drug can produce

Question 24

Partial Agonists

Answer 24

less efficacy than full agonists

Question 25

Potency

Answer 25

Amount of drug needed for a given effect

Question 26

Competitive Antagonist

Answer 26

shifts curve to right (decreases potency), no change in efficacy. Can be overcome by increase conc of agonist

Question 27

Noncompetitive Antagonist

Answer 27

Shifts curve down to decrease efficacy.

Cannot be overcome with increase agonist substrate

Question 28

Irreversible competitive antagonist

Answer 28

Shifts curve down to decrease efficacy.

Cannot be overcome with increase agonist substrate

Question 29

Partial Agonist

Answer 29

Acts on same site as full agonist but with lower efficacy. Potency is variable.

Question 30

Therapeutic Index

Answer 30

Measurement of Drug Safety

between ED50 and TD50 on graph or = TD50/ED50

Question 31

High Therapeutic Index

Answer 31

safer drug

Question 32

Low therapeutic Index

Answer 32

more dangerous drug

Question 33

LD50

Answer 33

median lethal dose

Question 34

TD50

Answer 34

median toxic dose

Question 35

Therapeutic Window

Answer 35

measure of clinical drug effectiveness

Question 36

ED

Answer 36

effective dose