Tutorial 6 - Clopidogrel and Genotyping

Question 1

How is Clopidogrel metabolised?

Answer 1

Clopidogrel is a prodrug, metabolised into its active state by CYP2C19

Question 2

What is clopidogrel resistance?

Answer 2

When no benefit is observed from taking clopidogrel, likely because the patient is a poor or intermediate metaboliser

Question 3

Name 3 limitations of genotyping CYP2C19 to predict the response to clopidogrel

Answer 3

1. Other factors will affect response such as body weight and interactions with other medications
2. May have rare a CYP2C19 variant that is not tested for and so not detected
3. It is possible that variants in other genes affect the response too

Question 4

Name 3 techniques that can be used to genotype CYP2C19

Answer 4

Sanger sequencing
Taqman allelic discrimination assay
Multiplex HRM assay

Question 5

Name 4 positive economic implications of genotyping CYP2C19 before prescribing clopidogrel

Answer 5

1. Save prescriptions for poor/intermediate metabolisers
2. Save amount of drugs prescribed for ultra rapid metabolisers
3. Less treatment needed for adverse effects
4. Results remain relevant for life and for other medications

Question 6

Name 4 negative financial implications of genotyping CYP2C19 before prescribing clopidogrel

Answer 6

1. Training/paying staff to carry out the test
2. Use of laboratories and materials to carry out the test
3. Educating clinicians about how to use and interpret the tests
4. False negatives/positives