Effect of Anticoagulant Therapy upon Aspirin-Induced Gastrointestinal Bleeding

ASPIRIN has been shown to cause gastro-intestinal bleeding. Although the blood loss associated with the relatively small dosage that is customarily used is slight (usually well below 10 ml. per day),' there are some situations in which the safety of aspirin may be questioned. Such a situation is the administration of aspirin to patients who are simultaneously receiving anticoagulant therapy. Some authors have, in fact, recommended that such patients should not use salicylates in any form.2 3 In view of the increasing number of patients who are receiving anti-coagulants on a long-term basis, and the ubiquitous use of aspirin, it is important to know whether significant increase in gastro-intestinal blood loss occurs in the presence of this combination of agents. The present study was designed to evaluate the safety of salicylate ingestion in combination with anti-coagulation, under controlled conditions. In addition, the possible effect of salicylate in-gestion on the dosage of anticoagulant needed to produce satisfactory levels of hypopro-thrombinemia was studied. Method The group under study consisted of sixteen men and nine women who were patients on the medical wards of St. Luke's Hospital. These patients, whose ages ranged from 31 to 85, were receiving acenocoumarin* to prevent complications of coronary artery disease, thrombophlebitis, and atrial fibrillation. Erythrocytes were labeled with sodium radio-chromate and reinjected according to a previously described method, and fecal blood content was calculated from the ratio of fecal:blood radioactivity .4 Prothrombin time was determined by the Link-Shapiro modification of Quick's method.5 When stable acenocoumarin dosage and prothrom-bin activity levels were attained, a 3-day quantitative stool specimen was collected and measured for blood content, and the result was considered a control value. Each patient was then given aspirin, 600 mg. four times daily. After a 3-day interval to allow for intestinal transit time, a second stool specimen was similarly obtained and measured. (In a group of 131 normal volunteers, who were previously studied by the same technic, the mean daily control fecal blood content was 0.5 + 0.4 ml.,t whereas that during periods of aspirin administration of the same dosage, was 4.7 ± 4.1 ml.) In order to determine the effect of aspirin upon prothrombin activity, the average daily maintenance dosage of acenocoumarin was calculated both before and during the week in which aspirin was given. Results Fecal Blood Content Results were obtained for fecal blood loss in 20 patients for control periods, and for 188 patients …