S15) Pharmacovigilance

Question 1

What is pharmacovigilance?

Answer 1

• Pharmacovigilance is the process of identifying and then responding to safety issues about marketed drugs
• It involves surveying the safety of drugs and developing strategies to minimise the risk and optimise benefits

Question 2

What are the aims of pharmacovigilance?

Answer 2

• Identify previously unrecognised drug safety hazards
• Elucidate factors predisposing to toxicity
• Obtain evidence of safety so that a new drug’s uses may be widened
• ‘False positive’ adverse drug reaction

Question 3

What are the two types of ADRs?

Answer 3

• Type A
• Type B

Question 4

What characterises Type A ADRs?

Answer 4

• Exaggerated pharmacological response
• Predictable
• Dose dependent
• Common
• High morbidity, low mortality

Question 5

What characterises Type B ADRs?

Answer 5

• Not expected from known pharmacology
• Unpredictable
• Independent of dose
• Rare
• High mortality

Question 6

What are the limitations of pre-marketing clinical studies in identifying drug safety issues?

Answer 6

• Small number of patients treated
• Frequent exclusion of patients who might be at greater risk of ADRs
• Limited duration of treatment
• Restricted doses

Question 7

How can one identify ADRs?

Answer 7

• Spontaneous reporting
• Cohort studies
• Case control studies

Question 8

Describe the three steps involved in the spontaneous reporting of ADRs

Answer 8

⇒ Recognition of a possible ADR

⇒ Establishing possible causal relationship

⇒ Reporting observations

Question 9

What are the advantages of spontaneous reporting?

Answer 9

• Operates as soon as drug is marketed
• Involves all doctors
• Overlooks all drugs
• Inexpensive
• Continues indefinitely

Question 10

What are the limitations of spontaneous reporting?

Answer 10

• Delays in reporting
• Poor quality data
• Misleading reports
• No control group
• Gross under-reporting of possible ADRs

Question 11

Describe the two steps involved in cohort studies of ADRs

Answer 11

⇒ Identify group of patients exposed to drug

⇒ Observe to determine rate of occurrence of ADRs and outcomes

Question 12

Describe the four steps involved in case-control studies of ADRs

Answer 12

⇒ Select cases with the adverse event/disease

⇒ Match controls without the adverse event/disease

⇒ Compare exposure to “risk factor” i.e. drug

⇒ Calculate odds ratio

Question 13

What are the advantages of case-control studies?

Answer 13

• Good for rare ADRs
• Good when there is long latency
• Relatively low cost
• Indicate degree of increased risk

Question 14

What are the limitations of case-control studies?

Answer 14

• Requires a prior hypothesis
• Suitable database not often available
• Many biases
• Expertise
• Credibility

Question 15

What are the factors affecting the under-reporting of ADRs?

Answer 15

• Failure of patient to report ADR to their doctor
• ADR is too trivial
• Ignorance of reporting
• Lack of time
• Uncertainty of relationship of drug to presentation
• Relating to duration of marketed drug
• Experience and familiarity with the ADR