pharmocology 3 drug metabolism and interactions

Question 1

adverse drugs effects

Answer 1

Type A 
- pharmacological or toxic effect
Type B
- idiosyncrasy 
drug allergy

Question 2

drugs with low therapeutic index

Answer 2

• anticoagulant i.e. warfarin
• aminoglycoside antibiotics i.e. gentamicin
• anticonvulsants i.e. phenytoin

high risk of going into toxic concentrations

Question 3

adverse drug effect site of actions

Answer 3

1) localised
- asprin (mouth ulcers, GI irritation)
2) systemic
- majority of reactions

Question 4

adverse drug effects time course

Answer 4

1) acute toxicity
- narcotics
- single intake/rapid onset
2) sub acute toxicity
- repeated exposure (hours/days)
- tetracycline i.e. rental impairment
3) chronic toxicity
- repeated exposure (months /years)
- chemical carcinogenesis

Question 5

mechanisms of type A adverse effects

Answer 5

• for augmented
• exaggerated therapeutic responses
• secondary unwanted actions
• more predictable or anticipated effects

Question 6

mechanisms of type B adverse effects

Answer 6

• pharmacologically unexpected unpredictable or idiosyncratic adverse reactions
• immunologic (allergic or anaphylactic)
• idiosyncratic (qualitively abnormal adverse reactions that occur in a given individual and whose mechanisms is not yet understood)

Question 7

type A reactions what to look for

Answer 7

predictable mainly dictated by the dose given to the pt
- respiratory depression
cardiac toxicity

Question 8

what pharmokinetics can be targeted fro adverse effects of the drugs

Answer 8

• absorption
• distribution
• metabolism
• excretion

Question 9

when should antacids and iron preparation s be take

Answer 9

empty stomahc

decrease absorption by chelation

Question 10

what may cause abnormal drug metaboliums

Answer 10

effect on CP450 drug metabolising enzyme (induction or inhibition)
disease (rental or hepatic dysfunction)
inherited factors either phase 1 oxidation or 2 conjugation

Question 11

factors which affect renal excretion of drugs

Answer 11

1) kidney function
2) protein binding
3) urine pH
4) urine flow

Question 12

renal excretion of drugs controlled by

Answer 12

1) glomerular filtration
2) tubular secretion
3) tubular reabsorption

Question 13

type A vs B reaction

Answer 13

Pharmacologically predictable
A yes B no
dose dependan
A yes B no 
Incidence and morbidity 
high A low B
treatment 
decrease dose A B stop

Question 14

drug allergy characteristics

Answer 14

• delay after initial exposure
• precipitated with small doses of drug
• does not resemble normal pharmacology
• classical symptoms of allergic response

Question 15

drug allergy drug related factors

Answer 15

nature of the drug
degree of exposure
route of administration
cross sensitisation ie close structural chemical relationship with other drugs

Question 16

drug allergy host related factors

Answer 16

age
sex
genetic factors
diseases
previous exposire

Question 17

anaphylaxis mechansim

Answer 17

release of inflammatory mediators from mast cells to tissue oedema/damage

Question 18

signs and symptoms of anaphylaxis

Answer 18

SOB
lightheadedness
confusion
diarhoeaa
skin rash/hives
HR change

Question 19

tx for anaphylaxis

Answer 19

adrenaline
antihistamine
steroids
B2 antagonist ie bronchodilator

Question 20

drug drug interaction mechanisms and subdivisions

Answer 20

1) pharmaceutical
2) pharmacodynamic
3) pharmacokinetic
- absorption
- distribution
- metabolism
- excretion

Question 21

how are drugs metabolised in the liver

Answer 21

CP450 enuzyme

Question 22

drug drug interactions can either

Answer 22

Can lead to

1) no effect
2) beneficial effect
- eg using antagist and agonist together, produces an effect without the toxicity
3) toxic effect

Question 23

CYP3A induction

Answer 23

induction of enzyme activity particularly cytochrome P450

• Requires synthesis of new enzymes
• leads to loss of efficacy in the same dose

Question 24

what do enzyme inhibitors do with blood/drug conc levels

Answer 24

increase concentration of drug within blood levesl

Question 25

enzyme inducers

Answer 25

reduce concentration of drug in blood levels

metabolised faster therefore leads to faster excreation

Question 26

substrates which use cytochrome P3A

Answer 26

midazolam

Question 27

what does erthromycin do

Answer 27

inhibitor

increases the effect of eg warfarin by inhibition of CP450

Question 28

midazolam

Answer 28

inhibits CP3A

therefore increases the plasma concentration of teh drug

Question 29

st johns wort

Answer 29

extract from flower
enhances metabolism of drugs
reduces plasma levels by inducing CYP3A

Question 30

excessive dosage of LA effects

Answer 30

CNS stimulation by depressing inhibitory pathway

then CNS depression: leathargy , respiratory depression, unconcoisness,

Question 31

effect of CYP3A4 and benzodiazepines

Answer 31

inhibition (increase plasma levels)