Disposition of Drugs

Question 1

Stages of drug Disposition

Answer 1

1. absorption
2. distribution
3. biotransformation
4. excretion

Question 2

Factors Affecting Simple Diffusion

Answer 2

1. Concentration Gradient
2. Lipid solubility
3. Degree of ionization

Question 3

pka

Answer 3

pH at which a weak electrolyte is 50% ionized and 50% nonionized

Question 4

Ionization of a drug depends on?

Answer 4

1. pH of the drug
2. aka of the drug
3. pH of the medium (environment)

Question 5

The rate of diffusion depends on what?

Answer 5

Drugs cross biological membranes in the non-ionized form. (lipid soluble & do not carry electric charges) The rate of diffusion depends on the ratio between the non ionized form of the drug & the ionized form (N/I)

Question 6

Acidic drugs ionize in what kind of medium?

Answer 6

Alkaline medium

Question 7

Basic drugs ionize in what kind of medium?

Answer 7

Acidic medium

Question 8

Facilitated diffusion

Answer 8

carrier mediated transport that doesn’t need energy. (downhill movement)

Question 9

Example of facilitated diffusion

Answer 9

Movement of glucose across a muscle cell membrane by insulin sensitive glucose transporter is an example of facilitated diffusion

Question 10

Example of pinocytosis

Answer 10

Sequestration of amino glycoside antibiotics by renal tubular cells

Question 11

Drugs cross cell membranes mainly by what type of diffusion?

Answer 11

Simple diffusion

Question 12

Can charged drugs cross biological membranes?

Answer 12

No

Question 13

This type of drug can cross biological membranes

Answer 13

weak acidic or weak basic drugs cross biological membranes in the uncharged (non-ionized) form.

Question 14

T/F uncharged molecules more readily cross cell membranes than charged molecules

Answer 14

TRUE

Question 15

T/F

Answer 15

acidification of the urine accelerates the secretion of a weak base, pKa=8

Question 16

Does plasma protein binding prolong the half-life of the drug

Answer 16

YES

Question 17

poorly perfused tissues

Answer 17

bone & adipose tissue

Question 18

Moderately perfused tissues

Answer 18

muscle & skin

Question 19

highly perfused tissues

Answer 19

brain, liver, kidney & endocrine glands

Question 20

Tetracycline has an affinity to what type of tissues

Answer 20

Calcium in skeletal muscles (don’t give this medicine w/ cheese)

Question 21

Amino glycosides have an affinity to what type of tissue?

Answer 21

Kidney tissue

Question 22

Iodine has an affinity to what tissue?

Answer 22

Thyroid gland traps iodine

Question 23

what is the most common cognation reaction?

Answer 23

Conjugation to glucuronic acid

Question 24

Cats are deficient in

Answer 24

gmucuronly transferases (also in hydroxylation & dealkylation)

Question 25

Dogs lack what enzymes

Answer 25

acetylating enzymes

Question 26

Drug examples that have extensive first-pass effect

Answer 26

Lidocaine, propranolol & morphine

Question 27

Ruminants & horses have high levels of what enzymes

Answer 27

oxidative enzymes (birds lack these enzymes)

Question 28

Drug inhibitors

Answer 28

Ketoconazole (used w/ cyclosporin for dermatitis & it has a low safety margin & ketoconazole can inhibit some of the enzymes in cyclosporin), Chloramphenicol, cimetidine

Question 29

Drug enzyme inducers

Answer 29

Phenobarbital, phenylbutazone, griseofulvin, & rifampin