Drug Drug Interactions Flashcards

1
Q

What is defined as drug drug interaction?

A

Modification of a drug effect by prior administration of another drug, herb, foodstuff, drink

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2
Q

When has a drug interaction occurred

A

When the interaction between a number of drugs produces an effect which is different from the effect of their own direct functions

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3
Q

Define “object drug”

A

A drug whose activity is effected by drug interaction

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4
Q

Define Precipitant

A

The agent that precipitates drug interaction
Causes

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5
Q

Are drug drug interactions aways detrimental?

A

NO

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6
Q

What is common amongst all the drugs associated with serious interactions?

A

They all have a relatively low therapeutic index -can easily lead to profound toxicity

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7
Q

Who are the susceptible patients to drug drug interactions?

A

The elderly
The young
The critically ill
Patients undergoing complicated surgical procedures
Patients with chronic conditions (liver disease, renal impairment, diabetes mellitus, epilepsy, asthma)

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8
Q

What are the possible effects on the pharmacodynamic effect on a drug due to drug drug interactions?

A

Antagonistic interactions
Additive or synergistic interactions
Interactions due to fluid and electrolyte disturbances.

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9
Q

What are the possible effects on the pharmacokinetic effect on a drug due to drug drug interactions?

A

Alteration of ADME

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10
Q

How can the absorption of a drug be altered?

A

Formation of insoluble complexes
Altered PH
Altered bacterial flora
Altered GI motility

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11
Q

When is delayed absorption a hindrance?

A

When the drug has a short half-life or when we want high plasma levels quickly.

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12
Q

How do changes in pH affect absorption?

A

The degree of ionisation is dependant on pH.

Absorption is determined by the degree of ionisation.

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13
Q

Where are most oral medicines absorbed?

A

In the small intestine

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14
Q

What is the rate limiting step of oral drug absorption?

A

Gastric emptying

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15
Q

When does protein binding displacement occur and what pharmacokinetic factor does it affect?

A

Occurs in reduction in plasma protein binding of drug caused by presence of another drug.

Affects Distribution

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16
Q

What are the two most important proteins in the blood?

A

Albumin

Alpha - 1 glycoprotein

17
Q

Why does a drug with a protein binding of 99 percent have the potential to reach toxic levels very easily?

A

A 1% increase in displacement will lead to a doubling of free plasma levels

18
Q

What do the effects of enzyme induction depend on?

A

age, disease, concurrent drug therapy

19
Q

How are most drugs excreted?

A

In urine or bile

20
Q

Can pharmacodynamic interactions of a drug be changed due to the presence of another drug acting directly on the same receptor?

A

Yes, another drug can also act indirectly on another receptor

pharmacodynamic interactions are either direct, indirect, antagonistic or synergistic/agonistic

21
Q

When does drug interactions involving metabolism occur

A

One drug inhibits metabolism of another

22
Q

What are the different pharmacodynamic interactions

A

Direct
Indirect
Antagonistic
Synergistic/Agonistic

23
Q

What is an example of direct antagonism

A

Beta blockers such as atenelol block actions of beta agonists such as salbutamol

24
Q

What is an example of synergistic interaction

A

Two drugs with same pharmacological effect act on different receptors

25
Q

What is an example of indirect antagonism

A

Warfarin and NSAIDS
Non Steroidal Anti-Inflammatory Drugs