Disposition of Drugs - Exam 3

Question 1

disposition of drugs describes the

Answer 1

study of the movement of drugs in the body across biological membranes from the time of absorption to elimination

Question 2

disposition of drugs also known as

Answer 2

pharmacokinetics

Question 3

what are the 4 stages of drug disposition

Answer 3

absorption, distribution, biotransformation (metabolism), and excretion

Question 4

7 factors that affect disposition of the drug

Answer 4

biological cell membranes, [gradient], pump mechanisms, site of administration, total body water, plasma protein binding, disease

Question 5

4 properties of the cell membrane

Answer 5

phospholipid bilayer, proteins & carbs, cell junctions, aqueous pores

Question 6

4 mechanisms of transport of drug across cell membrane

Answer 6

passive diffusion, facilitated diffusion, active transport, pinocytosis

Question 7

properties of passive diffusion

Answer 7

most common, no energy required, [high] -> [low], hydrostatic pressure differences, H2O can carry small H2O soluble substances with it i.e.: eating a tablet

Question 8

transmembrane passive diffusion

Answer 8

through aqueous protein channels in cell membrane

Question 9

paracellular passive diffusion

Answer 9

filtration through intracellular aqueous pores, tissues with barrier mechanism (tight junctions) i.e.: BBB

Question 10

simple diffusion passive diffusion

Answer 10

movement through lipid membrane

Question 11

the majority of drugs move through the body via

Answer 11

simple diffusion

Question 12

properties of facilitated diffusion

Answer 12

carrier-mediated, [high] -> [low], faster than passive diffusion, no energy required, saturable, i.e.: glucose transport via insulin in muscle

Question 13

properties of active transport

Answer 13

carrier mediated, [low] -> [high], requires energy, symporter, antiporter, saturable, selective, competitive inhibition by co-transporters

Question 14

most abundant active transport pump in the body

Answer 14

primary active transport

Question 15

example of primary active transport pump

Answer 15

Na K ATPase

Question 16

example of secondary active transport pump

Answer 16

Na glucose transporter in renal tubules

Question 17

pinocytosis also known as

Answer 17

“cell drinking”

Question 18

what is pinocytosis

Answer 18

endocytosis where drug engulfs the drug molecules dissolved in H2O

Question 19

example of drug transport via pinocytosis

Answer 19

aminoglycoside antibiotics that can cause renal damage/toxicity

Question 20

2 examples of aminoglycosides

Answer 20

amikacin & gentamicin

Question 21

3 factors affecting simple diffusion

Answer 21

[gradient], lipid solubility, degree of drug ionization

Question 22

lipid membrane effect on drug diffusion

Answer 22

limits it

Question 23

higher lipid solubility of a drug =

Answer 23

faster crossing cell membranes (lipophilic)

Question 24

lipid partition coefficient

Answer 24

solubility of drug in lipid : solubility of drug in H2O

Question 25

non-lipid soluble drugs dependent on

Answer 25

molecular size (smaller the molecule = faster the transport through membrane pores)

Question 26

drugs cross biological membranes in what form

Answer 26

non-ionized

Question 27

rate of drug diffusion depends on

Answer 27

degree of ionization (nonionized form of drug : ionized form of drug or N/I)

Question 28

3 factors degree of ionization depends on

Answer 28

pH of drug, pKa of drug, pH of environment in vivo (blood, stomach)

Question 29

how is pH determined in environment

Answer 29

number of protons (H+)

Question 30

pH of a drug depends on

Answer 30

whether it acts like an acid or a base in a solution

Question 31

most drugs act as

Answer 31

weak acids/bases (weak electrolytes)

Question 32

pH of cell surface in stomach

Answer 32

7

Question 33

pH of stomach (gastric juice, HCl)

Answer 33

2

Question 34

what is pKa

Answer 34

pH at which 50% drug ionized & 50% nonionized

Question 35

most drugs act as weak acids/bases with pKa between

Answer 35

3 and 11

Question 36

higher N/I caused by

Answer 36

higher pKa of weak acid & lower pKa of weak base

Question 37

a weak basic drug is expected to

Answer 37

be excreted in milk in large quantities