Drug Movement

Question 1

how does the bulk flow of a drug travel in the body?

Answer 1

via the circulatory system

Question 2

how do drug molecules travel over short distances?

Answer 2

via diffusionn

Question 3

which type of drugs are more likely to diffuse across lipid bilayer membranes?

Answer 3

lipid soluble drugs

Question 4

which moves quicker - large or small drug molecules?

Answer 4

small

Question 5

name four ways by which small molecules can cross cell membranes

Answer 5

passive diffusion
facilitated diffusion
active transport
endocytosis

Question 6

how do small molecules cross membranes via passive diffusion?

Answer 6

either directly through the lipid or through pores

Question 7

how do small molecules cross membranes via facilitated diffusion?

Answer 7

via specialised carrier proteins that bind the drug on one side of the membrane, change shape and release it on the other side

Question 8

does diffusion (passive or facilitated) require energy?

Answer 8

no

does require a concentration gradient

Question 9

how do small molecules cross membranes via active transport?

Answer 9

via specialised carrier proteins

requires energy

Question 10

how can water soluble drugs enter cells?

Answer 10

via facilitated diffusion or active transport, requires specialised carrier proteins

Question 11

what is another name for endocytosis?

Answer 11

pinocytosis

Question 12

how does endocytosis work?

Answer 12

invagination of the drug in part of the membrane to form a small vesicle, which is then released inside the cell

Question 13

what is pKa?

Answer 13

the pH at which 50% of a drug is ionised and 50% isnt

Question 14

what equation can be used to determine proportions of ionised and unionised drugs in a given pH environment?

Answer 14

henderson hasselbach equation

Question 15

where are drugs that are weak acids absorbed?

Answer 15

stomach due to its low pH

Question 16

where are drugs that are weak bases absorbed?

Answer 16

intestines due to their higher pH

Question 17

what body compartment are small water soluble molecules located in?

Answer 17

total body water

Question 18

what body compartment are large water soluble molecules located in?

Answer 18

extracellular water

Question 19

what body compartment are large molecules and highly charged located in?

Answer 19

blood plasma

Question 20

what body compartment are highly lipid soluble soluble molecules located in?

Answer 20

adipose tissue

Question 21

what is the apparent volume of distribution (Vd)?

Answer 21

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

Question 22

how do you calculate Vd?

Answer 22

dose/[drug]plasma

Question 23

which drug requires a higher dose - one with a high Vd or one with a low Vd?

Answer 23

high = higher dose required of equal potency to show effect

Question 24

what is the most abundant plasma protein?

Answer 24

albumin

Question 25

what effect does plasma protein binding have on drug movement?

Answer 25

reduces availability of the drug for diffusion to the drug target organ