CPTP 2.4

Question 1

Explain how pharmacogenetic variation can influence the response to drugs

Answer 1

• Polymorphic expression of enzyme can alter enzyme activity and therefore levels of metabolism
• slow metabolisers possess a defective enzyme –> higher plasma concentrations of the parent drug –> lower concentrations of the metabolite –> may lead to exaggerated therapeutic response at normal doses –> may necessitate reduction in drug dose

Question 2

Clinical consequences of inhibition of drug metabolising enzymes

Answer 2

• Results in prolongation of drug action

- Increases pharmacological effect

Question 3

Clinical consequences of induction of drug metabolising enzymes

Answer 3

• Decrease drug effectiveness on chronic exposure

- Need to increase drug dose