Pharmacodynamics and Pharmacokinetics

Question 1

michaeles menten

Answer 1

velocity of rxn vs. [substrate]

Question 2

Km

Answer 2

= 1/2 Vmax

inversely related to affinity of enzyme for substrate

Question 3

Vmax

Answer 3

direct proportional to enzyme concentration

Question 4

lineweaver burke plot

Answer 4

1/V vs. /[S]

y-intercept = 1/Vmax
x-intercept - = 1/-Km

Question 5

slope of lineweaver burke

Answer 5

= Km / Vmax

Question 6

noncompetitive inhibitor

Answer 6

decreased Vmax
no effect Km
decreased efficacy

Question 7

competitive inhibitor - irreversible

Answer 7

no overcome by increasing [substrate]

decreased Vmax
no change Km
decreased efficacy

Question 8

competitive inhibitor - reversible

Answer 8

overcome by [S]

Vmax unchanged
increased Km

decreased potency

Question 9

bioavailability

Answer 9

fraction admin drug reaching systemic circulation unchanged

= F

IV - 100%
oral - typically

Question 10

volume of distribution =

Answer 10

Vd = amount of drug in body / plasma drug concentration

Question 11

Vd of different tissues

Answer 11

blood - low
ECF - medium
fat - high

Question 12

clearance =

Answer 12

CL = rate of elimination of drug / plasma drug concentration

V= Vd x Ke (elim constant)

Question 13

half life =

Answer 13

t1/2 = 0.693 x Vd / CL

Question 14

remaining after 1, 2, 3, 4 half lives

Answer 14

1 - 50%
2 - 25%
3 - 12.5%
4 - 6.25%

Question 15

loading dose =

Answer 15

LD = Cp x Vd / F

Cp - target plasma concentration at steady state
F - bioavailability

Question 16

maintenance dose =

Answer 16

MD = Cp x CL x t / F

Cp - target plasma concentration
CL -clearance
t - dosage interval
F - bioavailability

Question 17

LD and MD with renal and liver disease

Answer 17

MD - goes down
LD - no change normally

MD = maintenance dose
LD = loading dose

Question 18

zero order elimination

Answer 18

rate - constant regardless of desired [plasma] of drug

constant amount of drug eliminated per unit time

linear

Question 19

first order elimination

Answer 19

rate - proportional to [drug]

constant fraction of drug eliminated per unit time

exponential curve

Question 20

drugs eliminated with zero order elimination

Answer 20

PEA

phenytoin
ethanol
aspirin

Question 21

ionized species

Answer 21

trapped in urine - cleared faster

Question 22

weak acid elimination

Answer 22

trapped in basic environment

tx OD with bicarb

Question 23

weak base elimination

Answer 23

trapped in acid environment

tx OD with ammonium chloride

Question 24

weak acid drugs

Answer 24

phenobarbitol
methotrexate
aspirin
TCAs

tx OD - bicarb

Question 25

phases of drug metabolism

Answer 25

1 - reduction, oxidation, hydrolysis - CYP450
-yield polar, water soluble metabolites - may be active

2 - conjugation - glucuronidation, acetylation, sulfation
-yield very polar inactive metabolite - lost in urine

Question 26

slow acetylators

Answer 26

more side effects certain drugs

• decreased phase 2 metabolism
• intermediates build up

Question 27

efficacy

Answer 27

max effect drug can produce

represented by Vmax

partial agonist - lower efficacy

Question 28

potency

Answer 28

amount drug needed for given effect

EC50 - effective concentration for 50% max effect

• shift to left - more potent
• shift to right - less potent

Question 29

competitive antagonist

Answer 29

decreased potency - can be overcome

ex/ flumazenil - benzo antagonist

Question 30

noncompetitive antagonist

Answer 30

decreased efficacy - cannot be overcome

ex/ phenoxybenazmine - NE antagonist alpha receptors

Question 31

partial agonist

Answer 31

lower efficacy

Question 32

therapeutic index

Answer 32

measure of drug safety

TD50/ED50

median toxic dose vs. median effective dose

safer drug - higher TI