Drug Disposition

Question 1

What is the study of drugs in the body across biological membranes from the time of absorption until elimination?

Answer 1

disposition of drugs

Question 2

4 stages of drug disposition (pharmacokinetics):

Answer 2

Absorption
Distribution
Biotransformation
Excretion

Question 3

Why is it important to make sure dehydrated patients are rehydrated while getting medical treatment?

Answer 3

Dehydration affects the electrolyte pumps, which will cause decreased absorption of drugs.

Question 4

What are the factors affecting disposition of drugs?

Answer 4

Cell membranes
Concentration gradient
Pump mechanisms
Site of admin
Total body water
Plasma protein binding
Disease

Question 5

Type of transport that does not require ATP and involves movement down a concentration gradient and hydrostatic pressure differences across membranes. It is also the most common form of transport.

Answer 5

Passive diffusion

Question 6

Type of passive diffusion in which contents move through lipid membranes. The majority of drugs are moved through the body in this way.

Answer 6

Simple diffusion

Question 7

Type of transport in which no ATP is required, and movement occurs down a concentration gradient, but is faster because it is carrier-mediated.

Answer 7

Facilitated Diffusion

Question 8

Type of transport that uses ATP and a carrier to move contents from low to high concentrations (uphill movement)

Answer 8

Active transport

Question 9

What type of active transport involves the Na/K ATPase pump, the most abundant AT pump in the body?

Answer 9

Primary active transport

Question 10

What type of active transport involves cotransport of glucose along with Na+ in the renal tubules?

Answer 10

Secondary active transport

Question 11

Type of transport known as “cell drinking” in which a cell engulfs drug molecules dissolved in water.

Answer 11

Pinocytosis

Question 12

T/F: Pinocytosis can interfere with lysosomal function and cause lysosomal rupture.

Answer 12

TRUE

Question 13

What drug type is transported via pinocytosis and is known to cause renal toxicity due to sequestration in the renal tubules?

Answer 13

Aminoglycosides

Question 14

What are 3 factors that affect simple diffusion?

Answer 14

Concentration gradient
Lipid solubility
Degree of drug ionization

Question 15

A drug with higher lipid solubility will cross the membrane ______.

Answer 15

Faster

Question 16

How do non lipid soluble drugs cross cell membranes?

Answer 16

More dependent on small size to get through membrane pores.

Question 17

Drugs cross membranes in ______ form.

Answer 17

Non-ionized

Question 18

Non-ionized drugs will cross the cell membrane _____ than ionized drugs.

Answer 18

Faster

Question 19

Degree of ionization depends on what 3 factors?

Answer 19

pH of drug
pKa of drug
pH of env in vivo

Question 20

What does the lipid partition coefficient compare?

Answer 20

Lipid solubility to water solubility

Question 21

A higher lipid partition coefficient equals a _____ lipid solubility, therefore a ______ diffusion of the drug through biological membranes.

Answer 21

A higher lipid partition coefficient equals a HIGHER lipid solubility, and therefore a GREATER diffusion of the drug through biological membranes.

Question 22

What do we call the pH at which a weak electrolyte (acid or base) is 50% ionized and 50% nonionized?

Answer 22

pKa

Question 23

If drug A is 50% ionized and 50% nonionized at a pH of 6, what is the pKa of the drug?

Answer 23

6

Question 24

Acidic drugs will ionize in _____ environments and basic drugs will ionize in ______ environments.

Answer 24

Alkaline

Acidic

Question 25

NSAIDS are weak acids. Considering the environment requirements for ionization, are NSAIDS more likely to be absorbed in the stomach or small intestine?

Answer 25

Stomach, since weak acids will be more nonionized (ideal for diffusion) in acidic environments.

*NSAIDS will be more ionized in the more basic environment of the small intestine and will not be absorbed well.

Question 26

What is the formula for pKa of a weak acid?

Answer 26

pKa = pH + log N/I

Question 27

What is the formula for pKa of a weak base?

Answer 27

pKa = pH + log I/N

Question 28

For optimal diffusion of weak bases through membranes, a ______ pKa is better.

Answer 28

Lower

*equation features I/N (lower pKa means N is higher in the denominator)

Question 29

For optimal diffusion of weak acids through membranes, a ______ pKa is better.

Answer 29

Higher

*equation features N/I (higher pKa means N is higher)

Question 30

Quaternary ammonium drugs are mostly ionized so the only way to administer them for systemic use is:

Answer 30

Injection

*not able to diffuse through membranes and distribute