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PHARM2060 > Module 10* > Flashcards

Module 10* Flashcards

1
Q

What does ADR stand for?

A

Adverse drug reactions

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2
Q

What are adverse drug reactions?

A
  • Adverse drug reactions (ADRs) are the unintended and undesired responses from drugs.
  • Adverse drug reactions are an enormous societal health problem.
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3
Q

True or False: Canadian research suggests that 7.5% of hospital admissions in Canada are attributed to adverse drug reactions. This represents 185,000 people per year.

A

True

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4
Q

Adverse drug reactions can include what?

A
  1. Side effects
  2. Drug toxicity
  3. Allergic Reaction
  4. Idiosyncratic Reaction
  5. Carcinogenic Effects
  6. Mutagenic Effects
  7. Teratogenic Effects
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5
Q

What are side effects?

A
  • Side effects are secondary to the main therapeutic effect of the drug and are expected.
  • Side effects occur at normal therapeutic doses and are often unavoidable.
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6
Q

What are side effects due to/caused by?

A
  • Side effects are often due to poor specificity or selectivity of the drug.
  • Example: antihistamines act by blocking H1 histamine receptors to prevent the symptoms of allergy (i.e. runny nose, watery eyes). Side effects include drowsiness, dry mouth and urinary retention. In the figure you can see that histamine binding to the histamine receptor in sinuses causes vasodilation which results in runny nose and watery eyes. Antihistamines act by blocking the effect of histamine. Side effects occur when antihistamines bind to either histamine receptors or other receptors in the brain. This produces sedation, dry mouth and urinary retention. These are side effects of antihistamines.
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7
Q

What is drug toxicity?

A
  • Drug toxicity can be considered as any severe adverse drug event.
  • Drug toxicity is often mediated by overdose where patients unintentionally or intentionally take too much medication.
  • These types of reactions are often extensions of the therapeutic effect.
  • For example, a patient who takes too much insulin will experience hypoglycemia (low blood glucose
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8
Q

Drug allergies are mediated by what?

A

Our bodies immune system

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9
Q

How do allergic reactions occur?

A
  • Allergy requires a prior sensitization where a patient is exposed to the allergen (i.e. drug).
  • Upon subsequent exposure to the drug an allergic reaction will occur. During allergic reactions, mast cells release chemical mediators such as histamine.
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10
Q

Describe allergic reactions

A
  • Allergic reactions can vary from itching and rash, to life threatening anaphylaxis (bronchospasm, edema and severe hypotension).
  • The intensity of allergic reactions are independent of dosage size. Therefore small doses can produce severe allergy.
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11
Q

What are the most common drug classes that cause allergic reactions?

A

Very few drugs cause allergic reactions. The most common drug class to cause drug allergy are the penicillins. Sulfonamides (an antibiotic) and nonsteroidal anti-inflammatory drugs (NSAID) are also known to cause drug allergy.

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12
Q

Approximately what percentage of adverse drug reactions are related to drug allergy?

A

approx. 10%

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13
Q

What are idiosyncratic reactions?

A
  • These are reactions that occur rarely and unpredictably in the population.
  • Recent evidence suggests that genetic polymorphisms account for the majority of idiosyncratic reactions.
  • The majority of polymorphisms causing idiosyncratic reactions occur in drug metabolizing enzymes and drug transport proteins.
  • It is hoped that one day, routine blood test will be able to determine people at risk for idiosyncratic reactions due to genetic polymorphisms. This already occurs in some centres for the drugs warfarin and 6-mercaptopurine which are metabolized by CYP2C9 and thiopurine methyltransferase (TPMT) respectively.
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14
Q

What is the occurrence of the CYP2C9 polymorphism?

A

Approximately 15% of Caucasians have a polymorphism that decreases metabolism.

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15
Q

Describe the CYP2D6 polymorphism

A

10% of Caucasian and African Americans are poor metabolizers. These patients do not experience pain relief when they take codeine. Codeine is a prodrug that is metabolized by CYP2D6 to morphine.

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16
Q

Define prodrug

A

a biologically inactive compound which can be metabolized in the body to produce a drug.

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17
Q

List the genetic polymorphisms that cause idiosyncratic reactions

A
  • CYP2C9
  • CYP2D6 (Codeine)
  • TPMT
  • OATP1B1
  • G6PDH - Glucose 6-Phosphate dehydrogenases deficiency
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18
Q

Describe the TPMT polymorphism

A

Thiopurine methyltransferase (TPMT) – Approximately 10% of patients have decreased activity and 0.3% have no activity. Treatment with thiopurine drugs in patients with low or absent TPMT can result in life threatening bone marrow suppression.

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19
Q

Describe the OATP1B1 polymorphism

A

An uptake drug transporter in the liver. 15% of Asian and Caucasian patients have a polymorphism that decreases function. This leads to an increase in plasma drug concentrations. This polymorphism has been implicated in causing myopathy (muscle toxicity) in patients taking statin drugs.

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20
Q

Describe the G6PDH polymorphism

A

Glucose 6-Phosphate dehydrogenase deficiency (G6PDH) – An enzyme important in red blood cell metabolism. Deficiency is common in people of African and Middle Eastern descent. Patients with deficiency may have red blood cell hemolysis following treatment with certain analgesics (i.e. Aspirin) or anti-malarial drugs.

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21
Q

What does carcinogenic mean?

A

Carcinogenic means the ability of a drug to cause cancer.

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22
Q

Why is it difficult to determine if a drug is carcinogenic?

A
  • Determining whether a drug is carcinogenic is difficult because it normally takes years after the initial dose to appear.
  • Example. The drug diethylstilbestrol (DES) used to be prescribed to prevent spontaneous abortion in high risk pregnancies. Years later it was determined that the female offspring developed vaginal or uterine cancer.
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23
Q

How many drugs have carcinogenic effects?

A

relatively few

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24
Q

A drug is mutagenic when it is able to do what?

A

Alter our DNA (change DNA)

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25
Q

Often when a drug it mutagenic, it is also what?

A

carcinogenic or teratogenic

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26
Q

True or False: Sometimes drugs that are mutagenic are not carcinogenic or teratogenic.

A

True

These drugs may receive approval for use from regulatory agencies if there is sufficient evidence of safety from preclinical studies.

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27
Q

Drugs are tested for their potential as mutagens by what?

A

the Ames test

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28
Q

Describe the Ames test

A

The Ames test evaluates the ability of the test compound (i.e. a drug) to cause a mutation in specialized strains of bacteria.

29
Q

What are teratogenic drugs?

A

Drugs that produce birth defects or impair fertility

30
Q

What are birth defects?

A

Typically we think of birth defects as major physical malformations, but birth defects also include behavioural and metabolic defects.

31
Q

What percentage of birth defects are caused by drugs?

A

less than 1%

32
Q

Describe sensitivity of teratogens during fetal development

A
  • Sensitivity to teratogens changes during development.
  • Gross malformations typically occur when exposure to a teratogen is in the 1st trimester.
  • Teratogen exposure during the second and third trimesters usually disrupts function as opposed to gross anatomy.
  • Transfer of drugs across the placenta is thought to be greatest in the third trimester because as the placenta develops, the surface area for transfer between maternal and fetal circulation increases. In addition, the placental-fetal barrier becomes progressively thinner.
33
Q

What has categorized drugs according to their (teratogenic) risk?

A

The United States food and drug administration (FDA)

In Canada, we use this table as a guideline

34
Q

Describe category A of the FDA pregnancy risk table

A
  • Well controlled human studies have failed to show risk to the fetus during the 1st trimester
  • No evidence of harm later in pregnancy
35
Q

Describe category B of the FDA pregnancy risk table

A
  • Animal reproduction studies have failed to show harm to the fetus and there are no well controlled studies in pregnant women, OR
  • Animal studies have shown an adverse effect but well controlled studies in pregnant women fail to show any harm
36
Q

Describe category C of the FDA pregnancy risk table

A
  • Animal studies have shown harm to the fetus but there are no well-controlled studies in pregnant women
  • Potential benefits of the drug outweigh the potential risk
37
Q

Describe category D of the FDA pregnancy risk table

A
  • Clear evidence of risk to the fetus from studies in humans
  • Potential benefits of the drug outweigh the potential risk
38
Q

Describe category X of the FDA pregnancy risk table

A
  • Studies in animals and humans clearly demonstrate risk to the fetus
  • Risks of using the drug clearly outweigh the benefits
  • These drugs should never be used in pregnant women
39
Q

Most organ systems are only sensitive to teratogenic effects during the first trimester, which system is sensitive to teratogenic effects for nearly the entire process of pregnancy?

A

the central nervous system

40
Q

Describe organ specific toxicity

A
  • Many drugs exhibit toxicity to a specific organ.
  • Organ specific toxicity can occur to the kidney, lung, heart, liver, muscle and inner ear amongst others.
41
Q

The most common and important organ specific toxicity is observed where?

A

in the liver and heart

42
Q

What is the most common reason for an approved drug to be removed from the market?

A

Hepatotoxicity

Why? Remember the liver is the primary site of drug metabolism. Some drugs are metabolized to toxic metabolites which can then cause liver injury.

43
Q

Define hepatotoxicity

A

Liver toxicity

Hepatotoxicity is the medical term for damage to the liver caused by a medicine, chemical, or herbal or dietary supplement. Hepatotoxicity can be a side effect of some HIV medicines.

44
Q

True or False: No drugs known to be hepatotoxic are administered to patients.

A

False

Several drugs known to be hepatotoxic are administered to patients.

45
Q

All patients taking hepatotoxic drugs should be educated to look for signs of liver toxicity which include what?

A

jaundice (yellow skin), dark urine, light-coloured stool, nausea, and vomiting

45
Q

All patients taking hepatotoxic drugs should be educated to look for signs of liver toxicity which include what?

A

jaundice (yellow skin), dark urine, light-coloured stool, nausea, and vomiting

In addition, liver function tests should be performed by measuring blood levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT).

46
Q

What are aspartate aminotransferase (AST) and alanine aminotransferase (ALT)?

A

AST and ALT are liver enzymes that normally have a low concentration in the blood. When the liver is damaged, blood concentration of these enzymes increases.

47
Q

Drugs known to be hepatotoxic should be used with caution in which patients?

A

patients at high risk for hepatic disease (alcoholics), patients with hepatic disease, and patients taking other medications with known hepatotoxicity

48
Q

Describe the different components of an ECG

A

P-Wave: normal atrial depolarization.
QRS complex: rapid depolarization of the left and right ventricles.
T-Wave: repolarization of the ventricles.
U Wave: not always seen on an ECG.
QT Interval: Represents the time required for the ventricles to repolarize. A prolongation of the QT interval is a major risk factor for the development of torsades de pointes, a life-threatening form of ventricular arrhythmia.

49
Q

What is an ECG?

A
  • The electrocardiogram (ECG or EKG) shows the electrical activity of the heart. An ECG is obtained by placing electrodes on the skin and measuring the electrical activity that occurs with each heartbeat.
  • Each “bump” in the ECG represents a different event in the heart beat.
50
Q

How many drugs are known to prolong the QT interval of an ECG?

A

More than 100 drugs are known to prolong the QT interval and many have been removed from the market.

  • Drugs that prolong the QT interval should be used with caution in patients predisposed to arrhythmias such as the elderly, and patients who have bradycardia (slowed heart beat), heart failure, low potassium or congenital QT prolongation.
51
Q

Are men or women more at risk of QT interval prolongation?

A

Women are at higher risk than men because their normal QT interval is longer.

52
Q

Define drug withdrawal

A

the unpleasant physical reaction that accompanies the process of ceasing to take an addictive drug.

53
Q

Describe the consequences (symptoms) or rapid drug withdrawal of opiates

A

Anorexia, irritability, nausea, vomiting, weakness, muscle spasm

54
Q

Describe the consequences (symptoms) or rapid drug withdrawal of benzodiazepines

A

Anxiety, insomnia, sweating, temours, panic delirium, paranoia, convulsions

55
Q

Describe the consequences (symptoms) or rapid drug withdrawal of beta blockers

A

Rebound hypertensions, chest pain myocardial infarction, arrythmia

56
Q

What are the three classes of drugs that typically need to be withdrawn slowly to avoid adverse reactions?

A

Opiates, benzodiazepines, beta blockers

57
Q

If a medication error is caused by a health care professional, it is called what?

A

an iatrogenic error

58
Q

What are the most common cause of adverse drug reactions?

A

medication errors

59
Q

List the 5 main categories of medication errors

A
  1. Prescribing – Health care professional prescribes the wrong drug, wrong dose or wrong route.
  2. Dispensing – The prescription is correct, but the pharmacist dispenses the wrong drug.
  3. Administration – The health care professional administers the incorrect dose and/or drug. Note, a patient can also make this error.
  4. Patient education – Illiteracy or language barriers may cause the patient to not comprehend the instructions. The health care professional (doctor, nurse, and pharmacist) must work together to ensure all patients understand information about drugs.
  5. Patient – The patient understands the instructions but doesn’t follow them (i.e., misses doses, takes more medication than prescribed).
60
Q

What is another category of medication errors?

A

drug naming

61
Q

What are some reasons for drug naming medication errors?

A
  • Unfortunately, the naming of many drugs are similar.
  • Medication errors are likely to occur when drug names look and/or sound the same.
  • Confusion over drug names represents ~ 15% of all medication errors.
  • Poor handwriting, illiteracy and strong accents (english as a second language) increase the chance of this type of medication error.
62
Q

What can be another dangerous source of medication errors?

A

Abbreviations

63
Q

Describe the error prone abbreviation “IU”

A

IU=International Unit; Misread as IV or “10”; Write “Units”

64
Q

Describe the error prone abbreviation “q.d.”

A

q.d.=Every day; q.i.d – tail of “q” and period reads as “i”; Write “every day”

65
Q

Describe the error prone abbreviation “q.o.d.”

A

q.o.d.=Every other day; Mistaken q.d. Or q.i.d; Write “every other day”

66
Q

Describe the error prone abbreviation of trailing “0” after decimal point, i.e., 1.0 mg

A

Trailing “0” after decimal point
(i.e. 1.0 mg)=1 mg; Mistaken as 10 mg if decimal is missed; Do not use trailing zeros for doses expressed in whole units

67
Q

Describe the error prone abbreviation of leading “0” before decimal point, i.e., .5 mg

A

Leading “0” before decimal point
(i.e. .5 mg)=0.5 mg; Mistaken as 5 mg if decimal is missed; Use a zero before a decimal place when the dose is less than a whole unit

68
Q

Which two abbreviations are often mistaken for each other?

A

MgSO4=Magnesium Sulfate; Morphine Sulfate; Write “magnesium sulfate”

MS, MSO4=Morphine Sulfate; Magnesium Sulfate; Write “morphine sulfate”

PHARM2060 (16 decks)

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