pharmacology

Question 1

what is bioavailability

Answer 1

fraction of unchanged drug that reaches systemic circulation

Question 2

how do you calculate oral bioavailability

Answer 2

area under curve for IV drug =X
area under the curve for oral drug = Y
Y/X x100

Question 3

what is generic substitution

Answer 3

a different formulation of the same drug
considered equivalent to each other, e.g. neurofen VS Tesco ibuprofen

generics must have a bioavailability of 80-125% compared to the reference product

Question 4

what is a therapeutic substitution

Answer 4

a different drug with the same effect, i.e. assumed therapeutic equivalence

Question 5

what are the disadvantages of oral route

Answer 5

patient compliance
patient must be able to eat
variation in bioavailability

Question 6

what ways will an oral drug fail to enter the circulation

Answer 6

destroyed in gut
not absorbed
destroyed by gut wall
destroyed by liver

this can change depending on the patient

Question 7

what is an excipient

Answer 7

makes the tablet bigger

Question 8

what are binding agents for

Answer 8

binds the tablet together

Question 9

what are lubricants for

Answer 9

involved in manufacturing process

Question 10

what is the advantage of a drug in solution

Answer 10

quicker to absorb

Question 11

what is the main site of drug absorption

Answer 11

small intestine, due to large surface area and more neutral pH

Question 12

what routes can drug pass straight into the circulation

Answer 12

buccal/sublingual

rectal mucosa, no first pass metabolism

Question 13

in which ways can drugs cross cell membranes

Answer 13

diffuse directly through the lipid
transmembrane carrier protein

rarely: diffusion through aqueous pores and pinocytosis

Question 14

describe ionisation for weak bases

Answer 14

ionised in acidic pH

absorbed in the small intestine

Question 15

describe ionisation for weak acids

Answer 15

unionised in acidic pH

also absorbed in small intestine due to large surface area

Question 16

describe uptake of Levodopa

Answer 16

taken up from stomach and small intestine by a transport carrier

DOPA decarboxylase is present in gastric mucosa which breaks it down

Question 17

what can affect drug absorption in the GI tract

Answer 17

drugs that alter absorption e.g. antacids, laxatives, vasodilators, some antibiotics

intestinal diseases which affect absorption or motility
e.g. crohns or coeliacs

particle size

first pass metabolism

splanchnic blood flow

efflux pumps

diet

Question 18

how might intramuscular drugs enter the circulation

Answer 18

lipophilic drugs rapdidly
polar drugs by bulk flow
high molecular weight via lymphatics

Question 19

how do inhalation drugs work

Answer 19

enter via alveolar epithelium or bronchial mucosa

Question 20

what are the advantages of intranasal drugs

Answer 20

avoids first pass metabolism

ease, convenience and safety

Question 21

describe some drugs that can be given topically

Answer 21

corticosteroids
antihistamines
local anaesthetics

transdermal patches eg contraception, HRT, GTN, nicotine

Question 22

what are the key drug factors

Answer 22

lipid solubility, acidic/ basic, charge and size

Question 23

what are key biological factors

Answer 23

blood flow, surface area, enzymes, compartment ph

Question 24

what gastrointestinal diseases might affect drug absorption

Answer 24

diabetic gastroparesis
crohns
coeliacs

Question 25

what are cortiocosteroids used to treat

Answer 25

eczema