Adverse Drug Reactions and Drug Interactions

Question 1

What is an adverse drug reaction?

Answer 1

1. A response to a drug which is noxious, unintended, and occurs at doses normally used in humans for prophylaxis, diagnosis, or therapy of disease, or for the modification of physiological function

Question 2

What are risk factors for ADRs?

Answer 2

1. Age
2. Gender
3. Genetic factors
4. Multiple chronic medical conditions
5. Multiple prescribers (concurrent therapies)
6. Chemical characteristics
7. Dose
8. Duration and frequency

Question 3

What is an adverse drug event?

Answer 3

1. Any untoward medical occurrence that may present during treatment with a pharmaceutical product but which does not necessary have a causal relationship with this treatment
   e. g. An elderly patient taking a sedating drug takes a fall - this is an adverse drug event as the injury is a result of taking the drug

Question 4

What are predictable reactions?

Answer 4

1. A reaction that is part of the pharmacological profile of the drug
2. Predictable effects take place soon after drug is initiated or when medication dose is increased

Question 5

What are unpredictable reactions?

Answer 5

1. Reactions that include those that are immunologically mediated (immune system has become overactive), or genetic differences in drug metabolism, or a mechanism of action that is not known that results in unexpected effects

Question 6

What are the classifications of adverse drug reactions?

Answer 6

1. Type A (augmented) reactions - occur as a normal pharmacological profile of the drug and are dose related (predictable reactions)
2. Type B (bizarre) reactions - include unwanted effects due to inherited abnormalities and immunological processes (i.e. drug allergy)
   a) Often caused by immunological and pharmacological mechanisms
   b) As they are unpredictable and not related to drug dosage, they are difficult to prevent, resulting in high morbidity and mortality
3. Type C (continuous/chronic) reactions - those that occur as a result of long-term drug usage
   a) E.g. parkinsonism with phenothiazines
4. Type D (delayed) reactions - occur years after treatment has finished and may even occur in the offspring of the person given the therapy
   a) E.g. secondary cancer after treatment with a cytotoxic drug
5. Type E (End-of-use) reactions - occur when discontinuation of therapy is too abrupt
   a) e.g. withdrawal effects - delirium tremens from ceasing heroin intake abruptly

Question 7

What are the types of drug interactions?

Answer 7

1. Pharmacokinetic drug interactions - occur during absorption, distribution, metabolism, or excretion (blood concentration of a given drug may be altered)
2. Pharmacodynamic interactions - occur when action of one drug interferes with that of another drug (a drug’s effect at a given plasma concentration may be modulated)
   a) The effect of one drug is modified by the prior or concurrent administration of another drug

Question 8

What are ways to avoids ADRs?

Answer 8

1. Careful note taking
2. Considering non-drug treatment options (e.g. lifestyle factors)
3. Appropriate dosing (lowest effective dose)
4. Reviewing therapeutic goals and drug regimens
5. Awareness of ADRs
6. Avoiding polypharmacy
7. Patient education

Question 9

What are ways to avoid DIs?

Answer 9

1. Avoiding drug combinations where possible
2. Spacing the dosing to avoid interaction
3. Monitoring for early evidence of interaction
4. Improving patient education on drug interactions