Sat13November1123AM 4

The cytochrome P450 (CYP) isoenzymes are involved in the metabolism of many drugs used by the anaesthetist.

Which one of the following CYP enzymes is most likely to be subject to genetic variability leading to adverse drug reactions?

(Please select 1 option)

CYP2C19

CYP3A4 Incorrect answer selected

CYP2E1

CYP2D6 This is the correct answer

CYP2C9

Explanation

CYP2D6 is responsible for approximately 25% of phase-1 drug reactions.

There can be as much as a 1 000-fold difference in the ability to metabolise drugs by CYP2D6 between phenotypes, which may result in adverse drug reactions (ADRs).

CYP2D6 is responsible for metabolism of antiemetics, beta blockers, codeine, tramadol, oxycodone, hydrocodone, tamoxifen, antidepressants, neuroleptics, and antiarrythmics.

Patients who take drugs metabolised by CYP2D6 and who have poor CYP2D6 metabolism are more likely to have ADRs, whereas people with ultra-rapid CYP2D6 metabolism may have a decreased effect of a drug due to low plasma concentrations of these drugs.

All the other CYP enzymes are subject to genetic polymorphism but variants are less likely to lead to adverse drug reactions.

Answer Statistics

1

9%

2

37%

3

7%

4

43%

5

6%

Times answered: 270