drug interactions 2

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  • Created by: Rscottqub
  • Created on: 06-01-20 15:36
Drug-drug interactions are not the only types of interactions
drug- food/drink, lifestyle
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Drugs and cig smoke - PAH
polycyclic aromatic hydrocarbons
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PAH what do they do
they are lung carcinogens and potent inducers of CYP enzymes particulary CYP1A2
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CYP1A2
many drugs are substrates for this - if they are induced more drug is metabolised , decreased plasma levels, increased dose req
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If patient stops smoking
then a dose reduction may be required and monitoring
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example of drug affected by cig smoke
olanzapine
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smoking and oxygen
should not smoke when using oxygen - clothing and hair will burn more readily in o2 vs air . same applied to e.cigarettes
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alcohol and metronidazole
no alcohol, and no alcohol until 48hrs after course finishes. can cause flushing of face and neck, nausea due to acetylaldehyde accumulation
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cranberry juice and warfarin
mechanism unknown , 1 reported death
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grapefruit juice and simvastatin
inhibits CYP3A4 in gut wall - decreased metabolism of simvastatin- high plasma levels - toxicity
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antagonist interactions
direct competition of 2 drugs for the same receptor sites - decreasing the effect of one or both drugs
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what is used to treat warfarin OD
Vit K
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what is warfarin
anticoagulant - works by competitively inhibiting enzyme involved in vit K sysnthesis .
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Vit K
is involved in clotting
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INR
international normalised ratio
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INR formula
patient PT/ control PT PT - prothrombin time
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the higher the INR
the longer takes for blood to clot
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INR of patient not on warfarin
1
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patient on warfarin INR
2-3 , this means it takes x2/3 times longer for blood to clot
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how does vit K reverse effects of warfarin
if vit K intake increased - overpowers warfarin as a competitive inhibitor - vit K helps blood clot - INR decreased
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where will you find Vit K
leafy greens , avocado etc
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how to manage warfarin OD treatment
monitor INR adjust dose of warfain
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Naloxone and opioids
naloxone = opiod antagonist reverses opioid toxicity
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how long does it take to reverse
2mins i.v
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half life naloxine
1-2 hours - need to monitor and give another injection if required
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targinact
oxycodone and naloxone - helps reduce constipation caused by oxycodone . Naloxone has greater affinity to opioid receptors vs oxycodone . NB it will not affect pain control of oxycodone
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managment if use naloxone
monitor for repeat injection req? if patient is opioid dep. rapid reversal can induce withdrawal symptpms
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additive interactions
2 drugs administered at same time with similar pharm effect . ie. co-codamol. Not strictly an interaction
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example 1- Enoxaparin + DOACS
using both will increase risk of bleeding
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DOACS
newer anticoagulants - apixaban, rivraoxaban
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should we use both enoxapain and DOACS
NOOOOO
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when moving from enoxaprain to DOACs
stop enox. and start DOAC on next scheduled of the enox
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if both administered inadvertedly
stop enox !! observe for bleeding . monitor . must inform patient . complete incident report form
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additive example 2- ACE inhib + spirolnoctlactone
increased risj of hyperkalaemia
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how to mangae
use lowest effective dose of both. if hyper occurs discontinue treatment
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drug/NT uptake example - MAOIs and tyramine food
can cause life threatning hypertension
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tyramine food
aged cheese, yeast extracts like marmite, beer, wine , caviar soy sauce
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also pseudoephrenines
COLD REMEDIES - not be used with MAOIS
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mechanims
MAOIs reduce NA breakdown - huge build up of NA , then released in synaptic cleft --> sympathetic overactivity --> hypertension, heart attack, intercranial haemmor.
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managment
counsel patietns on diet restrictions and cold remedies
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Other cards in this set

Card 2

Front

Drugs and cig smoke - PAH

Back

polycyclic aromatic hydrocarbons

Card 3

Front

PAH what do they do

Back

Preview of the front of card 3

Card 4

Front

CYP1A2

Back

Preview of the front of card 4

Card 5

Front

If patient stops smoking

Back

Preview of the front of card 5
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