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Exam 2019 > Interactions > Flashcards

Interactions Flashcards

1
Q

Name the enzyme inhibitors (SICKFACES.COM)

A 
Sodium valproate
Isoniazid
Cimetidine
Ketoconazole
Fluconazole
Alcohol (acute, binge)
Chloramphenicol
Erythromycin
Sulphonamides
Ciprofloxacin
Omeprazole
Metronidazole

Also:
Grapefruit juice

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2
Q

Name the enzyme inducers (SCRAP GPS)

A 
Sulphonylureas
Carbamazepine
Rifampicin
Alcohol (chronic)
Phenytoin

Griseofulvin
Phenobarbital
St John’s Wort

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3
Q

What are the main interactions with amiodarone?

A
  1. Amiodarone inhibits warfarin metabolism- enhanced anticoagulant effect
  2. Increased risk of bradycardia, AV block, myocardial depression with beta blockers
  3. Risk of ventricular arrhythmias with lithium
  4. Plasma concentration of digoxin increased by amiodarone

Amiodarone has a very long half life so there is potential for drug interactions to occur weeks/months after stopping treatment

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4
Q

What are the common interactions with digoxin?

A
  1. Plasma conc of digoxin increased by amiodarone
  2. Plasma conc of digoxin increased by erythromycin (enzyme inhibitor)
  3. . Plasma conc of digoxin reduced by rifampicin (enzyme inducer)
  4. Plasma conc of digoxin reduced by St John’s Worst (enzyme inducer)
  5. Increased toxicity of digoxin if hypokalaemia occurs with loop and thiazide diuretics
  6. Plasma conc of digoxin increased by CCBs
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5
Q

What are the common interactions with lithium?

A
  1. Risk of lithium toxicity with ACEi (excretion reduced)
  2. Risk of lithium toxicity with NSAIDs (excretion reduced)
  3. Sodium depletion with loop and thiazide diuretics (excretion of lithium reduced)
  4. Risk of ventricular arrhythmias with amiodarone
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6
Q

What are the common interactions with methotrexate?

A
  1. Increased risk of infection with vaccines
  2. PPIs at high doses reduce clearance of methotrexate increasing risk of toxicity
  3. Penicillins increases risk of methotrexate toxicity
  4. Trimethoprim- both folate antagonists, increased risk of side effects and nephrotoxicity
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7
Q

What are the common interactions with phenytoin?

A
  1. Effects of phenytoin enhanced by NSAIDs
  2. Amiodarone inhibits phenytoin metabolism
  3. Phenytoin accelerates metabolism of warfarin
  4. Cimeditine inhibits metabolism of phenytoin
  5. Plasma conc of phenytoin increased by fluoxetine
  6. St John’s Wort reduces plasma conc of phenytoin
  7. Ciprofloxacin affects the concentration of phenytoin
  8. Decreases efficacy of combined contraceptive pill
  9. Phenytoin decreases exposure to NOACS
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8
Q

What are the common interactions with theophylline?

A
  1. Increased risk of convulsions with quinolones e.g. ciprofloxacin
  2. Plasma conc of theophylline reduced by St John’s Wort
  3. Plasma conc of theophylline reduced by rifampicin
  4. Plasma conc of theophylline increased by cimetidine
  5. Plasma conc of theophylline increased by fluconazole
  6. Smoking can increase theophylline clearance and increased doses of theophylline are therefore required
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9
Q

What are the common interactions with warfarin?

A
  1. Anticoagulant effect increased by NSAIDs
  2. Anticoagulant effect increased by fluconazole
  3. Anticoagulant effect increased by statins
  4. Anticoagulant effect increased by ciprofloxacin, erythromycin, metronidazole
  5. Anticoagulant effect reduced by griseofulvin
  6. Anticoagulant effect reduced by antiepileptics
  7. Alcohol effects anticoagulant control
  8. Anticoagulant effect antagonised by Vitamin K
  9. Anticoagulant effect enhanced by cranberry juice
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10
Q

What is the risk of consuming tyramine based food and drink e.g. cheese if on MAOIs?

A

Hypertensive crisis

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11
Q

How does alcohol interact with TCAs and mirtazapine?

A

Increased sedative effect

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12
Q

What are the main interactions with combined oral contraceptives?

A
  • Enzyme inducing drugs increase metabolism of contraceptives. Additional contraceptive precautions should be taken for 4-8 weeks after stopping treatment
  • Some ABX may reduce efficacy of the pill by impairing bacterial flora responsible for recycling ethinylestradiol e.g. ampicillin, amoxicillin, doxycycline. Additional precautions are required for duration of treatment and for 7 days after stopping
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13
Q

What are the main interactions with progesterone only contraceptives?

A

Efficacy reduced by enzyme inducers

Additional protection is needed for duration of treatment and 4 weeks after

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14
Q

What are the main interactions with sympathomimetics e.g. pseudoephedrine?

A
  • MAOI- hypertensive crisis

- Beta blockers- hypertension risk

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15
Q

What are the main interactions with Orlistat?

A
  • Orlistat reduces plasma conc of amiodarone
  • Anticoagulants- monitor
  • Acarbose for diabetes due to its GI effects
  • Reduces absorption of ciclosporin
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16
Q

What is a pharmacokinetic interaction?

A

These occur when one drug alters the absorption, distribution, metabolism, or
excretion of another drug, thus increasing or reducing the amount of drug available
to produce its pharmacological effects.

17
Q

What is a pharmacodynamic interaction?

A

This is where effects of one drug are changed by the presence of another drug at its
pharmacological site of action.

e.g. electrolyte imbalance, combined toxicity, antagonising effects

18
Q

What PPI does clopidogrel interact with and what would be an alternative?

A

Omeprazole and esomeprazole

Lansoprazole would be an alternative

Exam 2019 (21 decks)

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