Drug Interactions Flashcards

1
Q

Define the Object Drug?

A

The drug whose activity is effected by an interaction

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2
Q

Define the precipitant?

A

The agent which precipitates a drug interaction

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3
Q

Give a case of a drug interactions that isn’t detrimental?

A

Parkinsonism is treated wiht levodopa & carbidopa.

The carbidopa prevents the systemic side effects of levodopa

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4
Q

What are the 5 types of drug interaction?

A
  • Drug
  • Herbal
  • Food
  • Drink
  • Pharmacogenetic
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5
Q

List the patient specific risk factors for drug interaction:

A
  • Old Age
  • Concomitant Disease
  • Genetic Polymorphisms
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6
Q

List the drug specific risk factors:

A
  • Polypharmacy
  • Narrow Therapeutic Range
  • HIgh Doses
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7
Q

What other risk factors are there for drug interactions? [non drug or patient specific]

A
  • Multiple Prescribing physicians
  • Self-Prescription (both naughty doctors & over counter drugs)
  • Prolonged stays in hospital
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8
Q

Patients with what characteristics are most susceptible to severe (life threatening) drug interactions?

A
  • many meds
  • undergoing complex surgery
  • are elderly
  • are young
  • Critically Ill
  • Liver or renal impairment
  • Epileptic
  • Asthmatic
  • Diabetes Mellitus (diabetic)
    AEDtic
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9
Q

What are the characteristics of drugs involved in serious interactions?

A
  • Steep Dose-Response Curves
  • Narrow Therapeutic Indexs
  • Very high protein binding
  • Can Alter Renal Clearence
  • Induce/inhibit hepatic enzyme
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10
Q

Name some foods that can interact with drugs?

A
  • Veg (Boccoli, spinach, cabbage)
  • Herbals (ginseng, Green Tea)
  • ‘Misc’ (avocado, fish oil)
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11
Q

What are the 3 types of mechanisms for drug interactions?

A

Pharmacokinetic Interactions
Pharmaceutical
Pharmacodynamic

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12
Q

What are pharmaceutical interactions?

A

Those involving mixing two drugs in the same solution

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13
Q

What is a pharmacodynamic interaction?

A

Pharmacodynamic interactions are where one drug alters anothers effect at its site of action

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14
Q

What are the subtypes of pharmacodynamic interaction?

A

Additive/Synergistic or antagonistic

Direct or indirect

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15
Q

Whats the difference between direct & indirect pharamcodynamic interactions?

A

In direct interactions one drug alters the others effect directly by actin on hte same receptor.
In indirect interactions they act on different receptors.

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16
Q

How do synergistic interactions occur?

A

2 drugs with the same pharmacological effect acting on the same receptor are given concurrently

17
Q

What are the 4 areas affected by pharmacokinetic drug interactions?

A

Absorption
Distribution
Metabolism
Elimination/Excretion

18
Q

How do drug interactions affect absorption rates?

A
  • They can form insoluble complexes (erythromicin & iron)
  • Alter pH causing another drug to ionise
  • Drugs can effect GIT motility
  • One drug can alter bacterial flora
19
Q

How do drug interactions affect drug distribution?

A

One drug can displace a plasma protein-bound drug possibly causing a massive change in its bioavailability

20
Q

What normally protects pateints from protin-binding displacement interactions?

A

Metabolism & excretion

21
Q

How do drug interactions affect metabolism rates?

A
  • Inhibit the cytochrome P450 system in the liver

- Induces liver enzyme activity (takes weeks to build up)

22
Q

How do drug interactions affect elimination?

A

Some drugs affect Glomerular Filtration Rate or tubular secretion

23
Q

What do loop diuretics do?

A

Loop Diuretics increase tubular reabsorbtion