Pharmacology- Drug Movement in the Body

Question 1

pharmacodynamics

Answer 1

what the drug does to the body

Question 2

pharmacokinetics

Answer 2

what the body does to the drug

Question 3

Absorption

Answer 3

from site of administration and enters plasma

Question 4

Distribution

Answer 4

drug reversibly leaves the bloodstream and is distributed into interstitial and intracellular fluids

Question 5

Metabolism

Answer 5

drug transformation by metabolism by liver and other tissues

Question 6

Excretion

Answer 6

drugs and/ or their metabolites leave the body via urine, faeces or bile

Question 7

where are lipid soluble drugs most likely to diffuse across?

Answer 7

lipid bilayer membranes

Question 8

Ways in which small molecules cross the cell membrane

Answer 8

• passive diffusion
• facilitated diffusion
• active transport
• endocytosis

Question 9

Passive diffusion

Answer 9

Molecule goes directly through the lipid or aqueous pores formed by aquaporins which transverse the lipid bilayer

Many lipid soluble drugs cross cell membranes in this way

Question 10

Facilitated diffusion

Answer 10

Specialised carrier proteins which bind the drug on one side of the molecule, causing a conformational change. it then releases it on the other side.

doesn’t require energy; does require a conc gradient

Question 11

Active transport

Answer 11

drug moved via specialised carrier proteins.

requires energy and can move drug molecules against the concentration gradient

Question 12

Endocytosis/ pinocytosis

Answer 12

invagination of part of the membrane

drug is encased in a small vesicle then released inside the cell

Transport of large drugs across the cell membrane eg B12

Question 13

Which type of transport can show saturation kinetics?

Answer 13

facilitated diffusion and active transport

Question 14

Principle sites of carrier mediated drug transport

Answer 14

• blood brain barrier
• GIT
• placenta
• renal tubule
• biliary tract

Question 15

proportion of ionisation of a drug depends on which 2 factors

Answer 15

pKa of the drug and local pH

Question 16

pKa

Answer 16

pH at which 50% of the drug is ionised and 50% is unionised

Question 17

For most drugs, which form are they in to be able to permeate the membrane?

Answer 17

non-ionised

Question 18

Henderson-Hasselbalch equation and its purpose

Answer 18

determine proportions of ionised and unionised drugs in a given pH environment

pKa=pH+log(AH/A-)

pH-pKa=log(A-/AH)

Question 19

Where do weak bases accumulate?

Answer 19

compartments with low pH

Question 20

Where to weak acids accumulate?

Answer 20

compartments with high pH

Question 21

Where are weak acids absorbed?

Answer 21

in the stomach due to its low pH

Question 22

Where are weak bases absorbed?

Answer 22

in the intestine, due to its higher pH

Question 23

Where does most oral route drug absorption occur?

Answer 23

small intestine due to its large surface area

Question 24

what do people in the pharmaceutical field look into?

Answer 24

developing devices for drug delivery and release into the optimal physiological environment to facilitate drug absorption

Question 25

Which compartment are small water soluble molecules delivered to?

Answer 25

total body water

Question 26

Which compartment are large water soluble molecules delivered to?

Answer 26

extracellular water

Question 27

Which compartment are highly plasma protein-bound molecules, large molecules, highly charged molecules
delivered to?

Answer 27

blood plasma

Question 28

Which compartment are highly lipid soluble molecules delivered to?

Answer 28

adipose tissue

Question 29

Apparent volume of distribution (Vd)

Answer 29

the extent to which a drug partitions between plasma and tissue compartments

Vd= dose/[drug]plasma

Question 30

how to determine Vd from drug blood plasma conc

Answer 30

administer drug dose, obtain sample, separate RBC and plasma, assay fro [drug]plasma, calculate Vd

Question 31

where are drugs with a decreased Vd generally retained?

Answer 31

vascular compartments

Question 32

where are drugs with an increased Vd generally retained?

Answer 32

adipose, muscle and other non-vascular compartments

Question 33

For drugs with equal potency, will a drug with a high Vd require a higher or lower dose than that of a low Vd?

Answer 33

Higher dose

Question 34

The most abundant plasma protein

Answer 34

Albumin

Question 35

How do most drugs bind to albumin?

Answer 35

with low affinity via electrostatic and hydrophobic forces

Question 36

What does plasma protein binding reduce?

Answer 36

Reduces the availability of the drug for diffusion to target organ

may also reduce transport of drug to non vascular compartments

Question 37

What happens to [drug]plasma as Vd increases

Answer 37

it decreases