Pharmacokinetics

Question 1

volume of distribution =

Answer 1

amount of drug in body/plasma drug concentration

Question 2

low Vd means drug distributes to:

Answer 2

intravascular compartment

Question 3

medium Vd means drug distributes to:

Answer 3

ECF

Question 4

high Vd means drug distributes to:

Answer 4

all tissues (including fat)

Question 5

clearance

Answer 5

• volume of plasma cleared of drug per unit time

- (0.7)(Vd)/(t 1/2)

Question 6

bioavailability

Answer 6

fraction of administered drug reaching systemic circulation unchanged

Question 7

How many half lives does it take for a drug to reach steady state?

Answer 7

4-5 (time to steady state depends ONLY on t 1/2 of the drug)

Question 8

In renal or liver disease, the ______ dose remains unchanged but the ____ dose decreases.

Answer 8

loading, maintenance

Question 9

Zero-order elimination

Answer 9

• rate of elimination is constant regardless of drug concentration
• constant amount of drug eliminated per unit time

Question 10

Key examples of zero-order eliminated drugs:

Answer 10

phenytoin, ethanol, aspirin (PEA in shape of 0!)

Question 11

First-order elimination

Answer 11

• rate of elimination is proportion to drug concentration

- constant fraction of drug eliminated per unit time

Question 12

Only ____ forms of drug can be reabosorbed.

Answer 12

neutral (uncharged)

Question 13

Weak acids get trapped in ____ environments.

Answer 13

basic

Question 14

Weak bases get trapped in ____ environments.

Answer 14

acidic

Question 15

pH > pKa

Answer 15

deprotonated

Question 16

pH < pKa

Answer 16

protonated

Question 17

Phase I metabolism

Answer 17

• reduction, oxidation, hydrolysis via CYP450

- yields slightly polar, water-soluble metabolites that are often still active

Question 18

Phase II metabolism

Answer 18

• conjugation (glucoronidation, acetylation, sulfation)
• yields polar, inactive metabolites
• preserved in geriatrics

Question 19

efficacy

Answer 19

maximal effect a drug can produce (Vmax)

Question 20

potency

Answer 20

amount of drug needed for given effect (more potent = less of it needed) (Km)

Question 21

competitive antagonists change ____ but not ____.

Answer 21

Km, Vmax

Question 22

noncompetitive antagonists change ___ but not ____.

Answer 22

Vmax, Km

Question 23

partial agonists change ____ and changes in ____ are variable depending on mechanism

Answer 23

Vmax, Km

Question 24

therapeutic index

Answer 24

TD50/ED50 –> want it to be VERY large to be a safe drug

Question 25

drugs with low therapeutic index

Answer 25

• theophylline
• quinine
• Li+
• digoxin
• immunoglycosides
• aminoglycosides
• phenytoin
• warfarin
• vancomycin

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