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Pre-reg COPY ~Iz > Interactions > Flashcards

Interactions Flashcards

1
Q

Phenytoin and Amiodarone

A

Amiodarone increases phenytoin concentration

NB: Amiodarone is an enzyme inhibitor.
Due to amiodarones long half life: potential for interaction several months after discontinuation

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2
Q

Phenytoin and Warfarin

A

Phenytoin (p450 enzyme INDUCER) induces warfarins metabolism, decreases warfarin concentration, reduced anti-coagulation effect, decreases INR

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3
Q

Phenytoin and COC

A

Phenytoin (a p450 enzyme inducer) accelerates metabolism of Oestrogens, reducing their effectiveness

Patient should be changed to an IUD

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4
Q

Phenytoin and Fluoxetine

A

Fluoxetine increases phenytoin concentration

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5
Q

Phenytoin and Theophylline

A

Theophylline decreases phenytoin concentration

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6
Q

Phenytoin and St Johns Wort

A

St Johns Wort decreases phenytoin concentration

St Johns Wort is an enzyme inducer

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7
Q

Phenytoin and Fluconazole

A

Fluconazole increases phenytoin concentration (Fluconazole enzyme inhibitor part of SICKFACES)

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8
Q

Phenytoin and Cimetidine

A

Cimetidine increases phenytoin concentration (Cimetidine enzyme inhibitor part of SICKFACES)

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9
Q

Phenytoin and Diltiazem

A

Diltiazem increases phenytoin levels, and diltiazems own effects are decreased by phenytoin

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10
Q

Phenytoin and Rate limiting CCB’s

A

Phenytoin decreases effects of Verapamil and Diltiazem and also Felodipine

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11
Q

Amiodarone and Grapefruit Juice

A

Grapefruit Juice increases levels of Amiodarone

Grapefruit Juice is an enzyme inhibitor

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12
Q

Amiodarone and warfarin

A

Amiodarone increases warfarin levels
Enhances anti-coagulant effects, increased bleed risk

Amiodarone is an inhibitor of some of the CYP450 enzymes.

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13
Q

Amiodarone and Simvastatin

A

Increased risk of Myopathy
Max dose of Simvastatin: 20mg

This is not the same with Atorvastatin etc but still monitor for mypopathy

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14
Q

Amiodarone and beta blockers and Rate-limiting CCB’s diltiazem and verapamil

A

Increased risk of
Bradycardia
Myocardial depression
AV block

When given with beta blockers/ rate limiting CCB

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15
Q

Amiodarone and Lithium

A

Increased risk of Ventricular Arrhythmias
(poss associated with QT prolongation)

Also both effect THYROID function

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16
Q

Amiodarone and Digoxin

A

Amiodarone increases plasma level of Digoxin, leading to digoxin toxicity

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17
Q

Theophylline + enzyme inhibitors:

Cimetidine, Fluconazole, Ketoconazole, Ciprofloxcin, Erythromycin

A

Theophylline levels increased as it is metabolised by the CYP450 enzymes

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18
Q

Theophylline + enzyme Inducers:
Carbamazepine, Alcohol, Phenobarbital, Phenytoin, Rifampicin, St Johns Wort
(SCRAP GP’s)

A

Theophylline levels decreased

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19
Q

Theophylline and Quinolone antibiotics e.g. Ciprofloxaxin, Levofloxacin

A

Increased risk of SEIZURES

These BOTH lower seizure threshold

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20
Q

What do diltiazem and Verapamil (rate limiting CCBs) do to Theophyllines concentration?

A

Increase it

these are CYP3A4 enzyme inhibitors!

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21
Q

NSAIDs and warfarin/ phenindione

A

NSAIDs increase warfarin levels- increased anticoagulant effect

NSAIDs, like warfarin, have a high affinty for Albumin. They displace warfarin off the protein= more free warfarin

So remember the interaction is not because both drugs can increase bleed risk- NSAIDs actually increase the levels of warfarin

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22
Q

SSRI’s and TCA’s and warfarin

A

SSRI’s and TCA’s will increase warfarin levels- increased anticoagulant effect

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23
Q

Statins and warfarin

A

Only statin that interacts: Rosuvastatin

Increased effects of warfarin

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24
Q

Clopidogrel and warfarin

A

Anti-coagulant effect enhance (both thin blood)- increased risk of bleeds

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25
Q

Orlistat + Antiepileptics

A

Possible increased risk of convulsions- orlistat lowers seizure threshold

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26
Q

Methotrexate and Phenytoin

A

Do not use together- both deplete Folate

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27
Q

Methotrexate and Trimethoprim/ Co-trimoxazole (trimethoprim + Sulfamethoxazole)

A

Do not use together- both deplete folate- haematological blood toxicity risk

Sulfamethoxazole also increases methotrexate toxicity

28
Q

Methotrexate and Ibuprofen

A

Methotrexate toxicity increased by NSAIDs due to decreased renal excretion

29
Q

Methotrexate and Flucloxacillin

A

Methotrexate toxicity increased by all penicillins due to decreased renal excretion

30
Q

Methotrexate and Clozapine

A

Neutropenia risk increased

31
Q

PPI’s and Methotrexate

A

Increased risk of Methotrexate toxcity as excretion decreased

32
Q

ALOT of antibiotics interact with Methotrexate. Can you think of any?

A

Trimethoprim/ co-trimoxazole (folate depletion)

The following increase methotrexate toxicity:
Ciprfloxacin 
Doxycycline
Tetracycline
Sulfonamide (Sulfamethoxazole)
33
Q

If in doubt, whats that ONE DRUG that seems to have interactions with everything?!

A

CICLOSPORIN

an immunosuppressant

34
Q

Which OTC medication can possibly interact with ANTI-EPILEPTICS and increase the risk of CONVULSIONS?

A

ORLISTAT (Alli)

35
Q

Carbamazepine is an enzyme inducer, but is itself metabolised by the CYP450 system. Which other enzyme inducers may reduce the concentration of carbamazepine?

A

Phenytoin (May also reduce phenytoins conc)
Rifabutin
St Johns Wort

36
Q

What drugs, used in hypertension, can increase the risk of Myopathy?

A

Diltiazem
Verapamil
Amlodipine
Ranolazine

MAX SIMVASTATIN DOSE= 20mg for all of these!!

37
Q

Drugs interacting with Gentamicin/ Vancomycin?

A

NEPHROTOXIC DRUGS:
Ciclosporin (immunosuppressant)
Tacrolimus (immunosuppressant)
Cephalosporins

OTOTOXICITY:
Loop diuretics (furosemide)
38
Q

What kind of OTC products should patients with high BP avoid?

A

SOLUBLE preparations e.g. effervescent

Due to high SODIUM content

39
Q

Spironolactone + ACEi/ARB

A

Potassium sparing diuretic given with postassium elevating drugs: HYPERKALEAMIA

40
Q

Spironolactone + Tacrolimus

A

Potassium sparing diuretic given with postassium elevating drug Tacrolimus: Hyperkaleamia

41
Q

Furosemide + Vancomycin

A

Increased risk of Ototoxicity

42
Q

Digoxin + Diuretics

A

Diuretics (thiazides and loops) can cause Hypokaleamia
Digoxin toxicity is precipitated by low potassium!!

Give potassium sparing diuretics/ potassium chloride to manage

43
Q

Eplerenone (potassium sparing diuretic) is metabolised by the CYP450 enzyme system

A

Its concentration is increased by clarithromycin and itraconazole only

Its concentration is reduced by all the enzyme inducers

44
Q

What drugs may cause hypoglyceamia and therefore reduce the amount of insulin a patient needs?

A

ACE inhibitors!

Other oral antidiabetics

45
Q

NSAID + quinolone (ciprofloxacin, Levofloxacin)

A

Possible increased risk of seizures

46
Q

NSAIDS are cautioned with other drugs increasing bleed risk. Can you think of any examples? (5)

A

SSRIs
Heparins
Dabigatran (NOAC)
Antiplatelets- clopidogrel, aspirin (itself is an NSAID)

47
Q

NSAID + Diuretics

A

Increased risk of nephrotoxicity

NSAIDs will also antagonise the diuretic effects: Fluid retention! Can cause ankle swelling and high blood pressure with chronic use

48
Q

NSAIDs + anti-hypertensives (beta-blockers, CCB’s, ACE inhibitors, alpha-blockers [tamsulosin, doxazosin] nitrates)

A

NSAIDs themselves can cause high BP

They antagonise the hypotensive effects of these drugs

49
Q

Which opioid can enhance the anticoagulant effect of coumarins (warfarin)

50
Q

Which antibiotic can reduce the effectiveness of most of the opioids, including fentanyl, morphine, codeine, methadone?

A

RIFAMPICIN!! (enzyme inducer)

51
Q

Opioids can reduce BP (hypotensive)
Their hypotensive and sedative effects are increased by alcohol.

What happens if given with MAOIs?

A

Possible CNS excitation or depression
Hypotension or hypertension can occur
(remember MAOIs can cause hypotensive crisis)

52
Q

Clopidogrel + enzyme inhibitors

A

Some of the enzyme inhibitors (erythromycin, cimetidine, ciprofloxacin, fluconazole, ketoconazole) actually REDUCE clopidogrels antiplatelet effect!- dont get confused in exam!

53
Q

Clopidogrel + PPI’s

A

Antiplatelet effect REDUCED by omeprazole and esomeprazole

Pantoprazole safest PPI to use, or H2 antagonist

54
Q

Sotalol + loop or thiazide diuretics

A

risk of ventricular arrhythmias caused by sotolol is increased by diuretics due to their hypokaleamia effect

55
Q

Lithium + ACE inhibitors

A

ACE inhibitors will decrease the excretion of lithium!

Nothing to do with electrolyte disturbance

56
Q

Lithium + Beta blockers

A

No interaction!

57
Q

Lithium + Aminophylline/ Theophylline

A

These will increase the excretion of lithium, reducing its levels

58
Q

NSAIDs + Lithium

A

Excretion of lithium reduced by NSAIDs so increased risk of Lithium Toxicity!

59
Q

Lithium + SSRIs

A

Increased risk of CNS effects, lithium toxicity

think SSRI’s cause hyponatreamia- sodium levels effect lithium

60
Q

Methotrexate and Aspirin

A

Methotrexate toxicity increased

As Aspirin and NSAIDs decrease methotrexate excretion

61
Q

Doxycycline + Isotretinoin

A

Severe headache/ visual disturbance due to cranial (brain) hypertension

62
Q

Atorvastatin and clarithromycin

A

increased risk of myopathy

63
Q

Co-trimoxazole + Spironolactone

A

Increased risk of hyperkaleamia

64
Q

Metronidazole + Mebendazole

A

severe skin reaction

65
Q

Baclofen + ACE inhibitors

A

Baclofen enhances hypotensive effect

66
Q

Baclofen + beta blockers

A

Baclofen enhances hypotensive effect

67
Q

Alpha blockers (sildenafil) + nitrates (isosorbide mononitrate)

A

Enhanced hypotension effects

Pre-reg COPY ~Iz (37 decks)

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