Table II.

Side effects of aspirin on the GI tract and related preventive measures.

Region affected	Main risk factors	Dose	Adverse drug reaction	Precaution
Upper GI tract	H. pylori infection and advanced age (>70)	LDA but the exact dose remains unclear.	UGSs, peptic ulcers and bleeding, perforation	PPI prophylaxis may be considered for patients with related risk factors (Fig. 1)
Lower GI tract	Older patients with a great number of comorbidities (122,123)	Even LDA was associated with damage (124) and increased doses can cause more severe bleeding (125)	Lower GI bleeding	Some studies have evaluated the efficacy of probiotics in preventing lower GI injury among patients treated with LDA, but there is insufficient evidence to recommend a specific probiotic (126,127).
Lower GI tract	Obesity, hypertension, anticoagulants, diabetes mellitus, and ischemic heart disease (16)	There is no dose-dependent effect but a greater risk with the increasing duration of regular aspirin use (98)	Diverticular bleeding and diverticulitis	There is no established prophylaxis for diverticular bleeding and diverticulitis.
Liver	Patients with hepatic dysfunction (99)	Dose-dependent, 75–300 mg/day does not result in liver damage	Hepatic injury (acute fulminant liver failure or with no symptoms but with the biochemical and histological characteristics of chronic active hepatitis)	Avoid large doses of aspirin.

GI, gastrointestinal; LDA, low-dose aspirin; PPI, proton pump inhibitor; H. pylori, Helicobacter pylori.