Topic 12 - Adverse Drug Reactions

Question 1

What are the classifications of ADRs?

Answer 1

Overdosing
Side effects
Secondary effects
Idiosyncratic reactions
Teratogenic effects
Immunological hypersensitivity reactions (allergic reactions)
Drug interactions

Question 2

What is frailty and polypharmacy?

Answer 2

In an aging population, there’s more people who are unhealthy with elderly taking 7+ drugs.
This has an effect on hospital admissions and economic burden.

Question 3

What are the causes of overdosing?

Answer 3

• Suicidal intent
• Failure to calculate dose correctly in adult and paediatric patients
• Failure to calculate dose correctly in those with renal/hepatic impairment

Question 4

Define side effect

Answer 4

Unwanted reaction due to the known pharmacological action of a drug

Question 5

What is secondary effects and can you give examples?

Answer 5

Secondary effect - something that occurs as a consequence of taking the drug but isn’t because of the pharmacological action of the drug.
E.g. inhaled corticosteroids for asthma can result in pseudomembranous candidosis
Antibiotics for chest infection can also cause candida albicans.

Question 6

What is an idiosyncratic reaction? Give an example.

Answer 6

Genetic predisposition to a rare effect of a medication.

E.g. GA can cause malignant hyperpyrexia in some people which can result in high body temp, metabolic acidosis and death. This is why it’s not done in GDP anymore.

Question 7

Define teratogenic effect and give examples of these and what they can do.

Answer 7

Teratogenic effect - a drug which shouldn’t be prescribed to pregnant women as it can result in damage to foetus or death to foetus.

Phenytoin - can result in cleft lip, learning difficulties.
Valproate - can result in congenital abnormalities (spina bifida) and developmental abnormalities
Mycophenolate mofetil - can result in congenital heart disease, and eye disorders
Tetracycline - can result in mottling of teeth and bones.

Question 8

Describe what happens in hypersensitivity reactions, what its dependent on and what classifications there are.

Answer 8

In hypersensitivity reactions, a drug molecule binds to a plasma protein and acts as a hapten, triggering an immunological response.

it is not dose dependent and small dose or second dose can cause it.

Classifications:
Class I - anaphylaxis
Class II - cytotoxic
Class III - antigen-antibody complex
Class IV - cell-mediated delayed

Question 9

Define drug interaction and what two types there are. Who is it most common in?

Answer 9

Drug interaction - the administration of drug A modifying the behaviour of drug B.

Two types:

• Pharmacodynamic - the administration of drug A affects the behaviour of drug B but not in the concentration of it in tissue fluid
• Pharmacokinetic - the administration of drug A affecting the concentration of drug B at target tissue/cells. ADME of one drug affected by administration of second drug.

Most common in the elderly.

Question 10

In terms of pharmacodynamic drug interactions, can you think of any synergistic/ additive drug reactions?

Answer 10

• NSAIDs and SSRIs can cause bleeding risk
• Warfarin/clopidogrel and aspirin can cause increased risk of haemorrhage
• Alcohol and opioids can result in drowsiness

Question 11

In terms of pharmacodynamic drug interactions, can you think of any antagonistic effects by adding a second agent?

Answer 11

• Aspirin and ibuprofen can be thrombogenic
• Oral hypoglycaemics and corticosteroids can lead to worsening HbA1c
• NSAIDs and antihypertensives can result in hypertension
• Adrenaline in LA and beta blockers can result in high BP.
• Adrenaline in LA and TCAs can result in high BP.

Question 12

Give examples of pharmacokinetic drug-interactions and how they work.

Answer 12

Absorption: