Drug interactions Flashcards

1
Q

Define a drug interaction

A

When effect of one drug are changed by presence of another drug, food, drink or other environmental chemical agent

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2
Q

What are the consequences of interactions?

A
  • Prevent correct treatment
  • Cause harm
  • Require expensive tests
  • Prolong hospital stay
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3
Q

Give an example of a useful interaction

A

Ace + diuretics

  • Synergistic for hypertension
  • Careful dose adjustments + blood monitoring
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4
Q

Give examples of a predisposing factor

A
  • Age (polypharmacy)
  • Co-existing disease
  • Race/genetic polymorphism
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5
Q

Pharmacokinetics

A
  • Absorption
  • Drug displacement
  • Metabolism
  • Excretion
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6
Q

Pharmacodynamics

A
  • Additive/synergistic interactions
  • Antagonistic interactions
  • Changes in drug transport
  • Changes in electrolyte balance
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7
Q

How long do enzyme inducers usually take for maximal effect?

A

1-3 weeks

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8
Q

How long do enzyme inhibitors usually take for maximal effect?

A

24 hrs

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9
Q

What are the gradings of severity listed in the BNF?

A
  • Severe: life threatening/permanent detrimental effect
  • Moderate: considerable distress/partially incapacitate, longterm effects
  • Mild: unlikely to cause concern/incapacitate majority of patients
  • Unknown: interactions predicted - insufficient evidence
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10
Q

What are the different levels of evidence listed in the BNF?

A
  • Study: based on formal study
  • Anecdotal: based on single case report
  • Theoretical: derived from in vitro studies
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11
Q

What are action messages?

A
  • Interaction will describe effect + action to be taken

- Included where combination is avoided, dose adjustment required or specific administration requirements

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12
Q

Give examples of drugs w/ a narrow therapeutic window

A
  • Warfarin
  • Digoxin
  • Anti-epileptics
  • Theophylline
  • Ciclosporins
  • Lithium
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13
Q

Give examples of drugs which require careful dosage control

A
  • Antihypertensive

- Antidiabetic

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14
Q

Give examples of enzyme inducers

A
  • Rifampicin
  • Phenytoin
  • Carbamazepine
  • Barbiturates
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15
Q

Give examples of enzyme inhibitors

A
  • Cimetidine
  • Ketoconazole
  • Ciprofloxacin
  • Erythromycin
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