Pharmocology Chapter 8

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Pharmacology
Chapter 8
Drug Interaction and OTC Drugs
updated 7 years ago by MeaganShanahan
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1

drug interaction

an altered or modified action or effect of a drug as a result of interaction with one or more other drugs.

2

adverse drug reaction

an undesirable drug effect that ranges from mild untoward effects to severe toxic effects, including hypersensitivity reaction and anaphylaxis

3

Drug incompatibility

a chemical or physical reaction that occurs among two or more drugs in vitro

4

Drug interactions can be divided into two categories

1) pharmacokinetic interactions and (2) pharmacodynamic interactions. These two categories of drug interaction are discussed individually.

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Pharmacokinetic interactions

are changes that occur in the absorption, distribution, metabolism or biotransformation, and excretion of one or more drugs.

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When a person takes two drugs at the same time, the rate of absorption of one or both drugs can change......

One drug can block, decrease, or increase the absorption rate of another drug. It can do this in one of the following three ways:

•By decreasing or increasing gastric emptying time
•By changing the gastric pH
•By forming drug complexes

7

Drugs that increase the speed of gastric emptying....

laxatives, metoclopramide) may lead to an increase in gastric and intestinal motility and cause a decrease in drug absorption.

8

Most drugs are absorbed primarily in the small intestine except.....

barbiturates, salicylates, and theophylline.

9

What drugs decrease gastric emptying time and gastrointestinal (GI) motility, thus causing an increase in absorption rate?

Narcotics and anticholinergic drugs (e.g., atropine) For those drugs that undergo gastric absorption, the amount or extent of absorption increases the longer the drug remains in the stomach.

10

What happens when gastric ph is decreased?

a weakly acidic drug is less ionized and more rapidly absorbed, example asprin

11

heavy-metal ions (calcium, magnesium, aluminum, and iron) found in antacids or iron may lead to the formation of a drug complex and thereby prevent the absorption of what antibiotic?

tetracycline.
Consequently, dairy products, multivitamins, and antacids should be avoided 1 hour before and 2 hours after tetracycline

12

when products that contain divalent cations are ingested with this type of antibiotics that may lead to the formation of a drug complex and thereby prevent the absorption?

fluoroquinolone antibiotics such as ciprofloxacin
Consequently, dairy products, multivitamins, and antacids should be avoided 1 hour before and 2 hours after.

13

Metabolism of this drug by gut bacteria serves to decrease its bioavailability

Digoxin, Consequently, the administration of one of these drugs Erythromycin, a macrolide antibiotic, and tetracycline are broad-spectrum antibiotics that destroy or inhibit the growth of these GI microflora. Consequently, the administration of one of these drugs to a client on digoxin therapy may lead to an increase in the absorption of digoxin and, ultimately, to toxicity.

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Gut bacteria are necessary to hydrolyze estrogen conjugates into free estrogens so that they may be optimally absorbed to exert their contraceptive effect. Concurrent antibiotic administration may alter these intestinal bacteria, thereby impairing this process and preventing the optimal absorption and effectivness of what?

oral contraceptives

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A drug's___________ to tissues can be affected by its binding to plasma/serum protein.

distribution

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two drugs that are____________ or _________ will compete for ________ in the plasma.The result is a decrease in protein binding of one or both drugs; therefore more _________circulates in the plasma and is available for drug action. This effect can lead to _________.

highly bound to protein,albumin,binding sites,free drug,drug toxicity

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xamples of drugs that are highly protein-bound include the anticoagulant_______ anticonvulsants such as _______ and ___________,most_____________, _________,__________ and_________________.

warfarin,phenytoin,valproic acid, gemfibrozil, nonsteroidal antiinflammatory drugs (NSAIDs)sulfisoxazole, glyburide, and quinidine

18

A significant decrease in the serum albumin level because of_________ and____________ can increase the free amount of highly protein-bound drugs such as phenytoin and warfarin, making more drug available to exert its pharmacologic effect.

liver disease and poor nutrition

19

Drugs that promote induction of enzymes are called

enzyme inducers

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Examples of enzyme inducers

Barbiturates such as phenobarbital are enzyme inducers.

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Phenobarbital increases the metabolism of most___________ and_________ Increased metabolism promotes __________ and _______ ____________ of the drug. The result is a decrease in drug action.

antipsychotics and theophylline,drug elimination anddecreases plasma concentration

22

The anticonvulsant drug __________ and __________ and the antimicrobial medication __________ are hepatic enzyme inducers that can increase drug metabolism

phenytoin carbamazepinee rifampin

23

A larger dose of __________ is usually needed while the client takes a hepatic inducer, because metabolism aids in decreasing the amount of drug.

warfarin

24

_______________increases hepatic enzyme activity and an increase theophylline clearance

Cigarette smoking

25

With ______________use, hepatic enzyme activities are increased; with use, metabolism is inhibited.

chronic alcohol, acute alcohol

26

Some drugs are __________ inhibitors

enzyme

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The antiulcer drug___________ is an enzyme inhibitor that decreases the metabolism of certain drugs such as theophylline. As the result of decreasing theophylline metabolism, there is an _________in the ___________ of theophylline. The theophylline dose needs to be decreased to avoid _________. O

cimetidine,increase ,plasma concentration,toxicity

28

Other well-known hepatic enzyme inhibitors are ______________ and _____________, an antifungal medication.

erythromycin, itraconazole

29

certain drugs, such as warfarin, digoxin, and theophylline induces the metabolism of what drugs?

...

30

Flavonoids, a group of naturally-occurring compounds found in the_____________ are potent inhibitors of the metabolism of carbamazepine, diazepam

juice and pulp of citrus fruits

31

What are the affects of a drug enzyme inducer?

Onset and termination of drug effect is slow, approximately 1 week.

Drug dosage may need to be increased with use of drug inducer.

Drug dosage should be adjusted after termination of drug inducer.

Monitor serum drug levels, especially if the drug has a narrow therapeutic drug range.

32

What are the affects of Drug enzyme inhibitor?

Onset of drug effect usually occurs rapidly.

Half-life (t½) of the second drug may be increased, causing a prolonged drug effect.

Interaction may occur related to the dosage prescribed.

Disease entities affect drug dosing.

Monitor serum drug levels, especially if the drug has a narrow therapeutic range.

33

Drugs can ________or__________ and have an effect on the excretion of other drugs

increase or decrease renal excretion

34

Drugs that decrease cardiac output, decrease blood flow to the kidneys, and decrease glomerular filtration can also_______________.

decrease or delay drug excretion

35

Two diuretics that decrease reabsorption of water, sodium, and potassium.

Furosemide (Lasix) hydrochlorothiazide (HydroDIURIL)

36

A renal loss of potassium, which may lead to a condition known as ________, can enhance the action of ________and _________ toxicity could occur

hypokalemia,digoxin,digitalis

37

Give examples of Two or more drugs that undergo the same route of excretion may compete with one another for elimination from the body.

Probenecid (Benemid) and Penicillin

38

Absorption :Laxatives

Speeds gastric emptying time

Increases gastric motility

Decreases drug absorption

39

Absorption Narcotics

slow gastric mobility

40

Absorption Anticholinergics

Decreases gastric motility

Increases drug absorption or decreases absorption depending on where the drug is delayed (gastric vs. intestinal)

41

Absorption Antacids

Increases gastric pH

42

Aspirin
Absorption

Decreases gastric pH

43

Distribution

Anticoagulant and antiinflammatory (sulindac)

Competes for protein-binding sites

Increases free drug (e.g., increases anticoagu

44

Absorption: Antacids and tetracycline

Forms drug complexes

Blocks drug absorption

45

Metabolism or biotransformation Barbiturates

Promotes induction of liver enzymes

Increases drug metabolism

Decreases drug plasma concentration of second drug

46

Metabolism or biotransformation

Antiulcer (cimetidine)

Inhibits liver enzyme release

Decreases drug metabolism of diazepam (Valium), phenytoin (Dilantin), morphine, and so on

47

Excretion Aspirin, ammonium chloride
Other: Decrease cardiac output and renal blood flow

Promotes excretion of weak base drugs (e.g., quinidine, theophylline

48

When two or more drugs are given together, one drug can potentiate or have a

synergistic effect

49

synergistic effect example

demerol and phenergan

50

When two drugs that have opposite effects, or ____________ effects, are administered together, each drug cancels the effect of the other. In other words, the actions of both drugs are nullified.

antagonistic

51

An example of an antagonistic effect occurs when the adrenergic beta stimulant _________ (Isuprel) and the adrenergic beta blocker __________ are given together

isoproterenol,propranolol (Inderal)

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TABLE 8-3 in book!! look at it :)

TABLE 8-3 in book!! look at it :)

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Table 8-5 look!!

Table 8-5 look!!

54

Food is known to ______, ________ or________ absorption.

increase, decrease, or delay drug

55

An example of food binding with a drug is the interaction of ____________ and dairy products. The result is a decrease in the plasma concentration.

tetracycline

56

Examples in which food increases drug absorption include the antibiotic_____________, the beta blocker and the cholesterol-lowering ___________. These drugs should be taken at mealtime or with food

nitrofurantoin (Macrodantimetoprolol (Lopressor), lovastatin (Mevacor)

57

The classic drug-food interaction occurs when an antidepressant of the __________________ is taken with tyramine-rich foods such as cheese, wine, organ meats, beer, yogurt, sour cream, or bananas. More _____________ is released, and the result could be a hypertensive crisis

monoamine oxidase inhibitor (MAOI) type (e.g., phenelzine,norepinephrine

58

Abnormal plasma or serum electrolyte concentrations can affect certain drug therapies, what drug therapies?

digoxin and there are decreased serum potassium and serum magnesium levels or an increased serum calcium level, digitalis toxicity may result. Drugs from the thiazide diuretic group can cause abnormal electrolyte concentrations.

59

Drugs from the thiazide diuretic group can cause abnormal electrolyte concentrations When taken with digitalis.. An example is hydrochlorothiazide (HydroDIURIL), which can decrease___________,____________and____________levels and can increase the serum calcium level. __________________ promotes potassium loss, and low serum potassium results in an increase in the uptake of digoxin by myocardial tissue.

serum potassium, magnesium, and sodium,Hydrochlorothiazide

60

A drug-induced ________________reaction is a skin reaction that is caused by exposure to sunlight.

photosensitivity

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there are two types of photosensitivity reactions: ______________ and________________.

photoallergy , phototoxicity.

62

___________________________occurs when a drug (e.g., sulfonamide) undergoes activation in the skin by ultraviolet light to a compound that is more allergenic than the parent compound. Because it takes time to develop antibodies, photoallergenic reactions are a type of delayed hypersensitivity reaction

Photoallergy

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__________________ a photosensitive drug undergoes photochemical reactions within the skin to cause damage. This type of reaction is different from photoallergy in that it is not immune-mediated. The onset of phototoxicity with erythema can be rapid, occurring within 2 to 6 hours of sunlight exposure

phototoxicity

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Examples of Photo toxicity table 8-6

Examples of Photo toxicity table 8-6