intro to pharmacology and therapeutics

Question 1

5 factors needed for prescribing

Answer 1

medicine, dose, route, frequency, duration

Question 2

what is pharmacodynamics

Answer 2

the study of biochemical and physiological effects of drugs on the body
‘what the body does to the drug’

Question 3

4 types of receptors

Answer 3

channel linked receptors
G protein coupled receptors
Enzyme-linked receptors
nuclear receptors (intracellular receptors)

Question 4

different targets of drug action

Answer 4

receptors, ion channels, enzymes, transporters

Question 5

4 drugs related to treatment of hypertension

Answer 5

atenolol - blocks response to noradrenaline
ramipril - prevents formation of vasoconstrictors
amlodipine - blocks calcium channels (important in vasoconstriction)
bendroflumethiazide - acts in kidneys reducing reabsorption of sodium

Question 6

drug dose response curve?

Answer 6

work out maximum response - Emax
ED50 (effective dose 50) - produces 50% of Emax

Question 7

what is therapeutic index?

Answer 7

gap between beneficial effects and adverse effects - difference between doses

Question 8

competitive vs non competitive antagonsists

Answer 8

competitive - block receptors
non-competitive - interfere with signal transduction mechanism

Question 9

what effects do antagonists have on dose response curves

Answer 9

increased dose for same effect - shift to right

Question 10

what is efficacy

Answer 10

the extent to which a drug can have its effect (greater Emax - high efficacy)

Question 11

what is potency

Answer 11

amount of drug required to have a specific effect (lower dose for same effect would have high potency)

Question 12

what is selectivity

Answer 12

receptors slightly different in different areas- different areas more or less likely to respond to same drug dosage

Question 13

desensitisation

Answer 13

response tails off over time

Question 14

gradual desensitisation over longer period of time?

Answer 14

tolerance

Question 15

rapid desensitisation over short period of time

Answer 15

tachyphylaxis

Question 16

causes of desensitisation - pharmocodynamic

Answer 16

reduction in receptor number
changes in receptor structure or function
exhaustion of mediators
physiological adaption

Question 17

reduced drug response other than pharmocodynamic reasons

Answer 17

altered physiology (eg gained weight)
disease progression
drug interactions
reduced adherence (bad drug giving by patients)

Question 18

pharmacokinetics?

Answer 18

what a drug does to the body

Question 19

what are the four stages of drug handling

Answer 19

absorption
distribution
metabolism
excretion

Question 20

how is pharmacokinetic handling of a drug influenced

Answer 20

physiological factors - age, sex, body, height
external factors - food, other drugs

Question 21

different oral routes?

Answer 21

swallowing
buccal - tablet between upper lip and gum
sublingual - tablet beneath tongue
buccan and sublingual involve drugs being absorbed into capillaries of oral circulation

Question 22

non oral routes of drug administration

Answer 22

intravenous
intramuscular
subcutaneous
inhaled
rectal
transderm

Question 23

pros and cons of intramuscular injection

Answer 23

rapid effect but rate of absorption highly dependent on muscle blood flow

Question 24

skin as a route of absorption?

Answer 24

transdermal - adhesive skin patches
topical - lotions/creams/etc

Question 25

what is bioavaliability

Answer 25

fraction of administered drug that reaches systemic circulation

Question 26

what is the most important limitation on absorption

Answer 26

'First pass' metabolism by enzymes in intestinal wall and liver

Question 27

gut enzymes?

Answer 27

monoamine oxidase L-aromatic amino acid decarboxylase cytochrome P450 isoform 3A4 phase 2 conjugating enzymes membrane transporters

Question 28

what system in the liver accounts for most first-pass metabolism of oral drugs

Answer 28

phase 1 metabolising enxymes of the cytochrome P450 system

Question 29

when is rectal administration useful

Answer 29

drugs used to soften faeces in constipated patients useful for patients who cannot swallow and there is no suitable injectable formulation

Question 30

features of intravenous injection

Answer 30

most direct route of entry, entire dose is bioavailable

Question 31

what is a low therapeutic index

Answer 31

narrow range between lowest effective dose and highest safe dose

Question 32

differences of peak concentration of oral and intravenous injection

Answer 32

lower and delayed for oral

Question 33

movement of drug molecules after absorption through different fluids

Answer 33

plasma to interstitial to intracellular fluid

Question 34

equilibrium and drug administration?

Answer 34

equilibrium will eventually be reached between plasma/interstitial/intracellular fluid. drug will be eliminated from plasma (metabolism or excretion) causing gradient moving drug out of tissues - unless further drug administration occurs

Question 35

what does distribution of drug molecules between compartments depend on

Answer 35

molecular size, lipid solubility, ionisation, binding to plasma proteins, rate of blood flow, special barriers, drug affinity for specific tissues

Question 36

how does the vast majority of drugs cross membranes

Answer 36

simple diffusion

Question 37

what does rate of transfer of drug molecules by diffusion depend on

Answer 37

concentration gradient, the molecule, the membrane

Question 38

how do drugs move across cell membranes other than passive diffusion

Answer 38

pore-mediated diffusion, pinocytosis

Question 39

what is pinocytosis

Answer 39

form of endocytosis. invagination of part of cell membrane, vesicle created which traps extracellular constituents within cell. contents released in cell or extruded by fusion with another membrane

Question 40

drugs that bind to plasma proteins? pros and cons?

Answer 40

aspirin, diazepam, phenytoin, warfarin. stay in body longer, less efficient distribution, lower therapeutic activity, less available for dialysis after toxic doses

Question 41

two phases of metabolism

Answer 41

phase 1 - non-synthetic - oxidation/reduction/hydrolysis phase 2 - synthetic - conjugation with natural endogenous constituent resulting in more soluble product easier to excrete

Question 42

factors effecting drug metabolism

Answer 42

genetics, age, sex, nutrition, disease, drugs, dose, route

Question 43

routes of drug excretion

Answer 43

faeces, bile, breath, sweat, urine, breast milk

Question 44

what must a drug be to be excreted

Answer 44

water-soluble

Question 45

mechanisms of renal excretion

Answer 45

glomerular filtration tubular secretion tubular reabsorption

Question 46

what is the law of mass action

Answer 46

the rate of a chemical reaction or process is directly proportional to the concentrations of the reactants

Question 47

first-order kinetics

Answer 47

constant fraction of remaining drug eliminated in a given time - usually 50% (half life)

Question 48

zero-order/saturation kinetics? drug examples?

Answer 48

concentration/time graph forms a straight line phenytoin, aspirin, paracetamol

Question 49

what are modified-release versions of medicines

Answer 49

release of drug in small bowel delayed so absorption occurs over longer period of time, prolonged effects

Question 50

hepatic extraction ratio?

Answer 50

high hepatic extraction ratio drugs will be extensively metabolised.

Question 51

what is the determinant of the rate at which steady state is achieved

Answer 51

half-life (not dose interval)