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Pharmacology II > Drug Interactions > Flashcards

Drug Interactions Flashcards

1
Q

Definition of drug interaction

A

Administration of one agent that modifies effect of a drug

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2
Q

5 agents that can cause drug interaction

A 
pharma. drug
recreational drug
environmental toxin
food
herbals
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3
Q

3 types of drug interactions

A

Pharmaceutical
Pharmacokinetic
Pharmacodynamic

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4
Q

When do pharmaceutical drug interactions happen?

A

Interactions occur prior to administration

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5
Q

Example of pharmaceutical drug interaction

A

Penicilin (-) and Aminoglycoside (+) make an insoluble precipitate

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6
Q

Pharmacokinetic drug interactions is due to a change of what?

A

Concentration in target tissue

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7
Q

Pharmacodynamic drug interactions alter what?

A

How tissue responds to drug in presence of agent

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8
Q

3 ways to prevent drug interaction

A
  1. Understand Drug mechanism
  2. Monitor blood levels of drugs with narrow therapeutic index
  3. Monitor parameters that may help characterize the early events of an interaction or toxicity
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9
Q

3 different pharmacodynamic interactions?

A

Same target
Same pathway
Complement pathway

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10
Q

In PK, drug interactions affect what?

A

Absorption (bioavailability)
Distribution
Metabolism (elimination)
Excretion (elimination)

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11
Q

The most pronounced PK drug interactions are those that affect ____________ and _______________

A

bioavailability and elimination

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12
Q

Absorption of drugs may be affected by concurrent use of other agents that…? (3)

A
  1. Bind or chelate
  2. Alter GI physiology
  3. Alter gut bacteria (enterohepatic circulation)`
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13
Q

What does cholestyramine do for hyperlipidemia?

A

In hyperlipidemic patients, cholesterol is precursor of bile salts in the intestines, but then gets reabsorbed into the liver.
Cholestyramine binds to salts and bile acids preventing the reabsorption from the intestines

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14
Q

Which drugs does cholestyramine bind with? (3) When should they be given if given together?

A

Digoxin
Warfarin
Tetracyclines
Drug should be given 1-2 hours before (or 4-6h after) cholestyramine

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15
Q

GI motility : what happens to absorption in a short vs. long transit time of food?

A

Short : incomplete absorption

Long : may delay absorption if it slows gastric emptying, may increase total absorption

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16
Q

What can increase transit time of food? (2)

A

Large meals and some drugs (morphine)

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17
Q

What can decrease transit time of food? (2)

A

Fasting

Laxatives

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18
Q

Ionized weak acid/bases : do they cross membranes easier or harder than nonionized?

A

harder

19
Q

The protonated form of weak acid/bases is at lower or higher pH?

A

Lower

20
Q

Is the protonated form of weak acids ionized or nonionized?

A

Nonionized

21
Q

Is the protonated form of weak bases ionized or nonionized?

A

Ionized

22
Q

Role of antacids? How does that affect the absorption of drugs that are weak acids/bases?

A

Increase gastric pH
Acids : decreases absorption
Bases : Increases absorption

23
Q

Distribution of drugs can be altered by agents that…? (2)

A

Compete for plasma protein binding or tissue binding

Alter barrier function

24
Q

3 drugs that are highly bound to plasma proteins and affect distribution?

A

Phenytoin
Tolbutamide for T2D
Warfarin

25
Q

Which drugs can reverse binding to plasma proteins and increase distribution?

A

Aspirin

Sulfonamides

26
Q

2 things that can reduce oral bioavailability, affecting GI metabolism and transport?
Elimination of these increases or decreases bioavailability?

A 
Drug transporters (PGP)
Metabolizing enzymes (CYP3A4)

Increases

27
Q

What food can inhibit cYP3A4 and PGP?

A

Naringin in citrus juices

28
Q

How many drugs are known to inhibit CYP3A4 and PGP?

A

85

29
Q

What is the affect of agents on barrier function?

A

Can inhibit efflux transporters (PGP) at barrier tissues and increase tissue bioavailability

30
Q

2 antifunguals that inhibit CYP3A4?

A

Itraconazole

Fluconazole

31
Q

Why are CYP3A4 inhibitors more efficient given orally than by IV? (2)

A

It goes through the enterohepatic pathway

CYP3A4 is in the epithelial cells of the GI tract

32
Q

Agents can have which effects on drug metabolizing enzymes?

A

Inhibit

Induce

33
Q

Two types of inhibition? How does this affect the binding?

A

Reversible : two agents compete for the active site of enzyme
Irreversible : bind with another agent rendering enzyme inactive

34
Q

CYP3A IRREVERSIBLE inhibitor has longer or shorter effect vs. reversible inhibitor? Delayed or faster effect?

A

Longer

Delayed

35
Q

What can increase gene expression of drug metabolizing enzymes? (2)

A

Many drugs

St. John’s wort

36
Q

What is the active ingredient in St. John’s wort?

A

Hyperforin

37
Q

Hyperforin and rifampicin :

  1. Activates what transcriptional regulator of CYP3A4?
  2. increase or decrease expression of CYP3A4?
  3. Does it increase or decrease drugs that are metabolized by CYP3A4?
A

PXR
Increase
Decrease

38
Q

Agents that can inhibit hepatic and renal drug transport can reduce what.
Can this become toxic? how?

A 
drug elimination (increases half-life)
Yes, depending on the site of interaction
39
Q

Example of transporter interaction?

A

Penicillin was needed during WWII.

Probenecid inhibits renal penicillin transport so they used that for the penicillin concentration to last longer

40
Q

What can affect urinary pH? This also influences what?

A

Drugs
Diet
Also influences renal excretion of weak acids and bases

41
Q

What happens to absorption of weak acids/bases when there is an alkaline pH?

A

increases reabsorption of weak bases

decrease reabsorption of weak acids

42
Q

Drugs are concentrated in ________ due to water absorption

A

Distal nephron

43
Q

Drugs that are nonionized are most likely to be reabsorbed ______

A

passively

Pharmacology II (21 decks)

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