pharmocology 3 drug metabolism and interactions Flashcards

1
Q

adverse drugs effects

A
Type A 
- pharmacological or toxic effect
Type B
- idiosyncrasy 
drug allergy
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2
Q

drugs with low therapeutic index

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

high risk of going into toxic concentrations

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3
Q

adverse drug effect site of actions

A

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

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4
Q

adverse drug effects time course

A

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

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5
Q

mechanisms of type A adverse effects

A
  • for augmented
  • exaggerated therapeutic responses
  • secondary unwanted actions
  • more predictable or anticipated effects
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6
Q

mechanisms of type B adverse effects

A
  • 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)
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7
Q

type A reactions what to look for

A

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

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8
Q

what pharmokinetics can be targeted fro adverse effects of the drugs

A
  • absorption
  • distribution
  • metabolism
  • excretion
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9
Q

when should antacids and iron preparation s be take

A

empty stomahc

decrease absorption by chelation

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10
Q

what may cause abnormal drug metaboliums

A

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

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11
Q

factors which affect renal excretion of drugs

A

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

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12
Q

renal excretion of drugs controlled by

A

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

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13
Q

type A vs B reaction

A
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
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14
Q

drug allergy characteristics

A
  • delay after initial exposure
  • precipitated with small doses of drug
  • does not resemble normal pharmacology
  • classical symptoms of allergic response
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15
Q

drug allergy drug related factors

A

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

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16
Q

drug allergy host related factors

A
age
sex
genetic factors
diseases
previous exposire
17
Q

anaphylaxis mechansim

A

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

18
Q

signs and symptoms of anaphylaxis

A
SOB
lightheadedness
confusion
diarhoeaa
skin rash/hives
HR change
19
Q

tx for anaphylaxis

A

adrenaline
antihistamine
steroids
B2 antagonist ie bronchodilator

20
Q

drug drug interaction mechanisms and subdivisions

A

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

21
Q

how are drugs metabolised in the liver

A

CP450 enuzyme

22
Q

drug drug interactions can either

A

Can lead to

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

23
Q

CYP3A induction

A

induction of enzyme activity particularly cytochrome P450

  • Requires synthesis of new enzymes
  • leads to loss of efficacy in the same dose
24
Q

what do enzyme inhibitors do with blood/drug conc levels

A

increase concentration of drug within blood levesl

25
enzyme inducers
reduce concentration of drug in blood levels | metabolised faster therefore leads to faster excreation
26
substrates which use cytochrome P3A
midazolam
27
what does erthromycin do
inhibitor | increases the effect of eg warfarin by inhibition of CP450
28
midazolam
inhibits CP3A | therefore increases the plasma concentration of teh drug
29
st johns wort
extract from flower enhances metabolism of drugs reduces plasma levels by inducing CYP3A
30
excessive dosage of LA effects
CNS stimulation by depressing inhibitory pathway | then CNS depression: leathargy , respiratory depression, unconcoisness,
31
effect of CYP3A4 and benzodiazepines
inhibition (increase plasma levels)