Moore and Goo conducted a study to assess morning and evening aspirin-induced damage to the gastric mucosa and to evaluate the protection offered by ranitidine in healthy male volunteers. Investigators evaluated the severity of gastric mucosal injury induced by aspirin (ASA) during morning and evening studies in 10 healthy, male volunteers. In a randomized, double-blind fashion, they were assigned to receive either ASA 1300 mg alone or ASA 1300 mg with ranitidine 150 mg or placebo during morning and evening studies. Each participant underwent 3 morning and 3 evening studies.Investigators determined the severity of damage caused by ASA on the basis of the number of punctate mucosal hemorrhages in the gastric antrum and low-body. Findings of the study -•    ASA led to gastric mucosal lesions in both morning and evening studies.•    There was marked intersubject variability in the severity or damage induced by ASA, ranging from 47 to 1030 lesions/subject in morning studies. •    Significant protection against ASA-induced lesions was offered by ranitidine.•    Significantly greater ASA-induced damage was evident in the morning studies, in comparison with the evening studies. The study suggested that mucosal resistance is higher in the evening and that ranitidine can protect against ASA-induced gastric mucosal injury.Source: Moore JG, Goo RH. Day and Night Aspirin-Induced Gastric Mucosal Damage and Protection by Ranitidine in Man. Chronobiology International 1987;4(1):111-116.