In acid-peptic disease, especially duodenal ulcer, these drugs reduce nocturnal acid secretion, accelerate healing, and prevent recurrences. Acute ulcer is usually treated with 2 or more doses per day, whereas recurrence of ulcers can often be prevented with a single bedtime dose. H2 blockers are also effective in accelerating healing and preventing recurrences of gastric peptic ulcers. Intravenous H2 blockers are useful in preventing gastric erosions and hemorrhage that occur in stressed patients in intensive care units. In Zollinger-Ellison syndrome, which is associated with gastrinoma and characterized by acid hypersecretion, severe recurrent peptic ulceration, gastrointestinal bleeding, and diarrhea, these drugs are helpful, but very large doses are required; proton pump inhibitors are preferred. Similarly, the H2 blockers have been used in gastroesophageal reflux disease (GERD), but they are not as effective as proton pump inhibitors (see Chapter 60).