Esomeprazole Magnesium (Nexium) is a proton pump inhibitor to reduce gastric acid secretion. The stability of Esomeprazole Magnesium is a function of pH; it rapidly degrades in acidic media, but it has acceptable stability under alkaline conditions. At pH 6.8 (buffer), the half-life of the magnesium salt is about 19 hours at 25°C and about 8 hours at 37°C. Recent randomized controlled trials in patients who are at moderately increased risk of ulcers have shown that the proton pump inhibitor Esomeprazole (the S-isomer of racemic omeprazole) reduces the gastroduodenal ulcer incidence by approximately 70-85% and the gastrointestinal bleeding risk by as much as 90%.