Table 1. Examples of gastrointestinal diseases with the therapeutic medications used and the polymorphisms in their metabolizing enzymes or targets.

Disease condition	Medication	Enzyme system
Inflammatory bowel disease	azathioprine	thiopurine S-methyltransferase
	6-mercaptopurine	thiopurine S-methyltransferase
Colorectal cancer	5-fluorouracil	dihydropyrimidine dehydrogenase/thymidylate synthase/xeroderma pigmentosum, complementation group D
	irinotecan	uridine diphosphate glucuronosyltransferase/carboxylesterase
	oxaliplatin	xeroderma pigmentosum, complementation group D/excision-repair, complementing defective, in Chinese hamster-1/glutathione S-transferase π-1
Colorectal adenoma	sulindac sulfide	flavin monooxygenase 3
	aspirin	uridine diphosphate glucuronosyltransferase 1A6