Histamine-2 Receptor Antagonist Versus Proton-Pump Inhibitor for the Prevention of Recurrent Upper Gastrointestinal Bleeding (UGI) in High-risk Users of Low-dose Aspirin (ASA)

No dose of "low-dose" aspirin (ASA) is safe in terms of the risk if ulcer bleeding. Even at a dose as low as 75 mg daily, ASA doubles the risk of ulcer bleeding when compared to the risk in non-users. This rise in the incidence was associated with a 44% increase in usage of ASA. In Hong Kong, ASA is also a major cause of peptic ulcer complications.

In the absence of safer aspirins, co-therapy with a gastroprotective drug remains the dominant preventive strategy. Given the vast number of people taking ASA, however, it is only cost-effective to identify and treat those who are at high risk of ulcer bleeding and who have a strong indication for ASA use. Data from observational studies and randomized trials have consistently shown that PPIs are effective in reducing the risk of ulcer bleeding associated with ASA. Other potential preventive strategies include eradication of H. pylori infection, substitution of ASA for other non-aspirin anti-platelet drugs, and co-therapy with misoprostol or H2RAs. Among these preventive strategies, co-therapy with a PPI for prevention of ulcer bleeding in high-risk ASA users remains the most studied and best proven strategy.

H2-receptor antagonists (H2RAs) are relatively weak acid suppressing drugs when compared to PPIs. Very few studies have evaluated the efficacy of H2RAs in the prevention of peptic ulcer bleeding with ASA. Two case-control studies yielded conflicting results with regard to the efficacy of H2RAs in reducing the risk of hospitalizations for ulcer bleeding with ASA. There is a limited data on the efficacy of H2RAs, however, our local health authority has endorsed the use of H2RA as a co-therapy in high-risk ASA users since 2001.

On the other hand, H2RAs have two potential advantages over PPIs. First, generic H2RAs are much cheaper than generic PPIs in Hong Kong. Second, unlike the interaction between PPIs and clopidogrel, concomitant use of H2RAs and clopidogrel is not associated with an increased risk of recurrent myocardial infarction. Thus, H2RA might be a cheap and safe gastroprotective drug in patients requiring dual anti-platelet therapy (i.e., ASA and clopidogrel) who require coronary stents.

In patients with acute coronary syndrome or acute ischemic stroke who develop ASA-induced bleeding peptic ulcers, whether ASA should be discontinued before ulcers have healed is a major dilemma. In another double-blind randomized trial, we have shown that discontinuation of ASA after endoscopic treatment of bleeding ulcers was associated with a significantly increased in mortality within 8 weeks.