Module 11 Flashcards

1
Q

Drug can interact with what?

A

Other drugs, food in our diet

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2
Q

The risk of drug interactions increases (almost _______) with what?

A

The number of medications a patient takes

increases almost linearly

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3
Q

Drug interactions are especially important in what cohort? Why?

A

Seniors - b/c the average 65 year old takes 7 medications

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4
Q

What is the most common type of drug-drug interaction?

A

Those affecting pharmacokinetics

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5
Q

When two or more drugs interact, there are 3 possible outcomes, these are?

A

1 - increased effects
2 - Decreased effects
3 - Generation of a new effect

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6
Q

Drug interactions can increase drug effects by either an increase in the _______ effect or an increase in ________ effects.

A

therapeutic

adverse

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7
Q

Describe an example of increased therapeutic effect from drug-drug interactions.

A

Sulbactam - inhibitor of the bacterial enzyme that inactivates ampicillin
Co-administration increases the therapeutic activity of ampicillin

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8
Q

Describe an example of increased adverse effects from drug-drug interactions.

A

Warfarin and aspirin coadministration - can lead to potentially life-threatening side effects

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9
Q

Give an example of a drug-drug interaction that reduces therapeutic effects.

A

Clopidogrel + omeprazole
Omeprazole inhibits CYP2C19 - which converts the pro-drug clopidogrel to its active metabolite - therefore anti-coagulation doesn’t occur to an appreciable amount

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10
Q

Give an example of a drug-drug interaction that reduces adverse effects.

A

Naxolone and morphine overdose

Naxolone is a competitive antagonist of morphine - prevents coma, respiratory depression or death from morphine OD

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11
Q

Give an example of a drug-drug interaction that generates a new effect.

A

Disulfiram inhibits acetaldehyde metabolism causing severe hangover-like symptoms within 10 minutes of alcohol consumption

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12
Q

What are the different types of drug interactions?

A

Direct physical interaction
Pharmacokinetic interaction
Pharmacodynamic interaction
Combined toxicity

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13
Q

Direct physical or chemical interaction of two or more drugs

A

Direct physical interaction

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14
Q

Interactions affecting ADME

A

Pharmacokinetic interactions

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15
Q

Interactions affecting receptor binding

A

Pharmacodynamic interactions

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16
Q

Two or more drugs exhibit toxicity to the same organ

A

Combined toxicity

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17
Q

The most common direct interaction occurs when?

A

When two or more IV solutions are mixed together

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18
Q

Often, mixing IV solutions causes a ________ to form.

IF this occurs, what should be done?

A

precipitate

in that case, throw it out

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19
Q

Drug solutions should never be mixed without consulting a _________ _______.

A

compatibility chart

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20
Q

Which drug should never be mixed with another drug?

A

Diazepam

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21
Q

Although direct drug interactions are more common when mixing medications, they may also occur following __________.
What is an example?

A

Administration

Sodium bicarbonate followed by calcium gluconate - form a precipitate in the blood

22
Q

By far the most common type of drug interaction experienced in patients.

A

Pharmacokinetic interaction

23
Q

What is the most common drug interaction with respect to alteration of pH?

A

Antacids - increase gastric pH and thus absorption of weak bases in the stomach

24
Q

Antacids dramatically affect the absorption of this type of formulation.

A

Enteric coated drugs - can get dissolved in the stomach as the pH is increased

25
Q

Describe chelation/binding drug interactions and give an example.

A

One drug binding another in the intestine.
Bile acid sequestrants usually bind intestinal bile and prevent their absorption in the intestine (cholestyramine) - binds to digoxin in the intestine, decreasing its absorption

26
Q

Describe an example of altered blood flow from drug-drug interactions.

A

Epinephrine (vasoconstriction) and a local anesthetic - decreases absorption - allows it to remain at the injection site for longer

27
Q

Describe how gut motility affects drug absorption and give two examples.

A

Laxatives increase gut motility and decrease drug absorption

Opiates decrease gut motility and increase drug absorption

28
Q

If vomiting occurs within ___-___ minutes of taking one or more medications, it is likely that absorption is incomplete.
However, when can toxicity occur?

A

20-30

IF the drug entered the intestine before the patient vomitted, adding more drug may cause toxicity

29
Q

Describe how drugs that kill intestinal bacteria affect absorption.

A

Intestinal bacterial mostly de-conjugate phase II drug metabolites and increase enterohepatic recycling.
Killing them off decreases plasma drug concentration

30
Q

Describe how both sodium bicarbonate and ammonium chloride affect pH.

A

sodium bicarbonate raises pH
Ammonium chloride decreases it
(extracellular pH)

31
Q

Describe a way in which sodium bicarbonate is used as a drug-drug interaction to alter pH.

A

Sodium bicarbonate raises pH extracellularly, and draws out aspirin into the ECF (used in OD cases)

32
Q

Describe how protein binding drug-drug interactions work.

A

The drug with the higher affinity knocks off the lower affinity drug, increasing the free concentration of the displaced drug

33
Q

One of the most important and common types of drug metabolism.

A

Altered drug metabolism

34
Q

Most drug-drug interactions affecting metabolism occur where?

A

the liver or intestine

35
Q

Increased synthesis of CYP enzymes

A

induction

36
Q

Induction is a ______ process, therefore it may take __-___ days following exposure to the enzyme inducer before induction occurs

A

delayed

2-10 days

37
Q

Once the inducer is stopped, it takes _-__ days before the CYP enzyme levels return to normal.

A

7-10

38
Q
For each of the following, describe their inductive effects.
Cigaretee/marijuana smoke
Rifampin
Phenobarbital
BBQ'd food
Alcohol
A

1 joint = same inductive effect as 5-10 cigs
Rifampin - induces CYP3A4
Phenobarbital induces many CYPs
BBQ’d food - induces CYP1A2
Alcohol induces CYP2E1 (cirrhosis decreases it however)

39
Q

Typcially, enzyme inhibition results in _______ plasma concentration of the parent drug.

A

increased

40
Q
Describe what enzyme is inhibited by the following.
Antibiotics/anti-fungals
HIV protease inhibitors
SSRIs
Fluvoxamine
Grapefruit juice
A
antibiotics/anti-fungals - CYP3A4
HIV protease inhibitors - CYP2C19
SSRIs - CYP2D6
Fluvoxamine - CYP1A2
Grapefruit juice - CYP3A4
41
Q

How does altered blood flow affect excretion?

A

Decreased renal blood flow means decreased filtration and thus excretion

42
Q

Give examples of drugs affecting blood flow and excretion.

A

NSAIDs cause renal vasoconstrictions

Beta blockers decrease Cardiac output

43
Q

Describe an example of altering pH in drug excretion.

A

In amphetamine overdoses (weak base), the pH of the renal filtrate is acidified by ammonium chloride

44
Q

Provide an example of drug-drug interactions affecting tubular secretion, and how it works.

A

Probenecid - a drug used to treat gout - blocks the transporters responsible for moving penicillin from the blood, into the tubule lumen
Thus, penicillin excretion decreases, and plasma concentration rises

45
Q

What are the two main types of pharmacodynamic drug interactions?

A

Interactions that occur at the same receptor

Interactions that occur at separate sites

46
Q

usually, drug interactions that occur at the same receptor are the result of an ________ blocking the action of an _______.

A

antagonist

agonist

47
Q

Describe an example of an interaction occuring at the same receptor used to treat drug overdose.

A

Naxolone - competitive antagonist - binds to receptors that morphine binds to

48
Q

Describe drug interactions that occur at separate sites.

A

Morphine and diazepam both are CNS depressants. Although they function on different receptors (opioid receptor and benzodiazepine receptor, respectively), the combination of their effects is enhanced CNS depression

49
Q

Give two examples of drugs that interact for combined toxicity.

A

Acetominophen and alcohol - both hepatotoxic

Isoniazid and rifampin - both used to treat TB and are hepatotoxic (both are usually necessary unfortunately)

50
Q

What foods must patients taking MOA inhibitors avoid?

A

Foods containing thyramine - aged cheese, yeast, red wine, sauerkraut, cured meat and soy sauce

51
Q

Why must patients avoid tyramine containing foods when taking MOA inhibitors?

A

MAO inhibitors inhibit the breakdown of tyramine

Tyramine causes increased NE release from peripheral nerve terminals and can cause potentially fatal HTN.

52
Q

What are symptoms of a HTN crisis caused by high tyramine levels?

A

Tachycardia, severe HTN, headache, nausea, and vomiting