Drugs affected by Pharmacogenetics

Question 1

omeprazole

Answer 1

Proton pump H+/K+ ATPase irreversible inhibitor in gastric parietal cells, suppress stomach acid secretion, treat peptic ulcer, GERD

hepatic elimination by CYP2C19

Has wide therapeutic index, unlikely to cause substantial toxicity in PM, prescribe anyways

Question 2

clopidogrel

Answer 2

Antiplatelet, used with aspirin after percutaneous coronary intervention i.e. stent, minimise risk of further thrombosis —> ischemia

a prodrug activated by CYP2C19

Don’t prescribe to PM

Question 3

codeine

Answer 3

pain relief

converts to morphine by CYP2D6

Don’t prescribe to UM and PM, prescribe normally to EM and IM, IM if no response try alternative e.g. morphine or nonopioid

Question 4

irinotecan

Answer 4

Inhibitor of DNA topoisomerase, cytotoxic, very narrow thrapeutic index, treat colorectal cancer
Adverse effect: neutropenia (low neutrophils)

eliminated by hepatic glucuronidation catalysed by UGT1A1

All patient starts at 400 mg dose (900 mg iv) and then escalate dose at next treatment to identify maximum tolerated dose for each genotype