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HMS120: Pharmacology > Drug Interaction > Flashcards

Drug Interaction Flashcards

1
Q

Define Drug interaction

A
  • When the pharmacological activity of one drug is altered by the concomitant use of another drug or by the presence of some other substances.
  • Interaction between a drug and another substance e.g. food
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2
Q

What is an Object drug?

A

Drug whose activity is affected by such as interaction.

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3
Q

What is a Precipitant?

A

Agent which precipitates such an interaction.

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4
Q

What does a drug interaction lead to?

A

An interaction that could manifest as an:

  • INCREASE or DECREASE in drug effectiveness.
  • ADVERSE REACTION or new SIDE EFFECT.
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5
Q

Give an example when drug interaction can be beneficial.

A

Penicillin and Probenecid enhances activity of Penicillin.

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6
Q

Factors contributing to drug interactions:

Many Malaysian People Are in Need of Drug M.

A

M - Multiple drug therapy and prescribers.
M - Multiple pharmacological effects of drug.
P - Poor patient compliance.
A - Advancing age of patient.
N - Narrow therapeutic index drugs e.g. Lithium, Digoxin, Warfarin.
D - Drug-related factors
M - Multiple diseases / predisposing illness.

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7
Q

The 6 Types of Drug Interactions:

A
  1. Drug-Food interactions
  2. Drug-Disease interactions
  3. Environment-Induced interactions
  4. Drug-Drug interactions
  5. Chemical-Drug interactions
  6. Drug-Laboratory test interactions.
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8
Q

Example of Drug-Food interaction

A

Mixing alcohol with some drugs may cause a feeling of tiredness or slows down reactions.

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9
Q

What further contributes to Drug-Food interaction?

A
  • Lack of standardization

- Contamination

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10
Q

Drug-Food interaction can result in…

A

Impaired nutritional benefit.

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11
Q

When do Drug-Disease interactions occur?

A

When an existing medical condition makes certain drugs potentially harmful.

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12
Q

Example of Drug-Disease interaction

A

High BP can cause unwanted reaction with nasal decongestant.

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13
Q

What is important for a physician to know?

A

Patient’s entire disease profile

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14
Q

What patients are prone to Drug-Disease interactions?

A
  • Frail elderly hospitalised patients

- Critically ill patients or Chronic diseased patients

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15
Q

Explain Drug-Disease Interactions

A
  • may occur when an existing medical condition makes certain drugs potentially harmful
  • can occur when medication has the potential to worsen disease
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16
Q

Example of Drug-Disease Interaction

A

high blood pressure can cause unwanted reaction with nasal decongestant

17
Q

Explain Environment-induced interaction

A
  • when there is an intentional or unintentional exposure to environmental chemicals that can cause pharmacokinetic and/or pharmacodynamic reactions
18
Q

Examples of Environment-induced interactions

A
  • smoking
    : carcinogenic polygenic aromatic hydrocarbon in tobacco smoke are potent INDUCERS of CYP4501A1/1A2 and possibly 2E1 enzymes

: pharmacokinetic interactions with smoking occur with drugs like caffeine (substrates of CYP1A2)

19
Q

Explain Drug-drug interactions

A
  • when two or more drugs interact with each other to produce pharmacokinetic and pharmacodynamic reactions
  • harmful drug-drug interactions are important as they cause 10-20% of ADR
20
Q

Example of drug-drug interactions

A
  • mixing drugs taken to sleep (sedatives) and drugs taken for allergies (antihistamines) can slow reactions and make driving dangerous
21
Q

Why are the elderly patients vulnerable to drug-drug interactions?

A
  • increasing age
  • number of drugs prescribed
  • frequency of potential drug-drug interactions
22
Q

Examples of top drug-drug interactions

A
  1. Warfarin - Non-steroidal anti-inflammatory drugs (NSAIDs)
  2. Warfarin - Sulfa Drugs
  3. Warfarin - Macrolides, Quinolones, Phenytoin
  4. ACE Inhibitors - Potassium Supplements and Spironolactone
  5. Digoxin - Amiodarone and Verapamil
  6. Theophylline - Quinolones
23
Q

Explain Pharmacokinetic drug-drug interactions

A
  • what the body does to the drug

- occur when one drug alters the concentration of another drug with clinical consequences

24
Q

Definition ADME interactions?

A

pharmacokinetic interactions (ADME interactions) occur when the absorption, distribution, metabolism or elimination process of the object drug is altered by the precipitant drug

25
Q

Resultant effect of ADME interactions?

A

altered plasma concentration of the object drug

26
Q

Explain drug absorption interactions

A
  • interactions where the absorption of the object drug is altered
27
Q

Where are interactions influencing absorption more likely to occur?

A

GI tract

28
Q

What are the net effect of drug absorption interactions?

A
  • faster or slower drug absorption

- more or less complete drug absorption

29
Q

What are clinically significant interactions that occur due to the drug absorption effect?

A
  • changes in GI pH and motility
  • changes induced by chelation and absorption
  • transporter based interactions
30
Q

Explain how alteration in GI pH affects drug absorption?

A
  • non-ionised = lipid soluble = more readily absorbed from GIT (than in ionised form)

: some drugs are absorbed from stomach (acidic media), so when the media becomes neutral or alkaline, drug absorption is affected

31
Q

Example of how alterations in GI pH can occur?

A
  • sulphanomides and aspirin when given with antiacids lead to enhanced dissolution
  • tetracycline with antacid leads to decreased dissolution
32
Q

How does drug interaction alter bacterial flora, ultimately affecting absorption?

A
  • bacterial flora has a marked role in metabolism of some drugs
    : long term antibiotics may kill normal flora and affect drug absorption

e. g. 40% or more of administered Digoxin dose in metabolised by the intestinal flora
- antibiotics kill a large population of intestinal flora, and thus increases the Digoxin concentration and chances of toxicity

33
Q

Define complexation

A

the covalent or non-covalent interaction between two or more compounds that are capable of independent existence

34
Q

Define chelation

A

a type of bonding where ions and molecules bind to metal ions

35
Q

How does drug interaction cause complexation and chelation, therefore affecting absorption?

A
  • drugs such as tetracycline / fluroquinolones with antacid / food contain divalent ions
    : lead to the formation of poorly soluble chelates or complexes which cannot be absorbed

e.g. warfarin and cholestyramine lead to reduced absorption due to binding

HMS120: Pharmacology (13 decks)

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