Prednisone and ultralow-dose aspirin: Good for the gut?

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An increasingly popular form of therapy for many conditions-most commonly immune-mediated hemolytic anemia but also systemic lupus erythematosus and membranous glomerulonephritis, among others-is combining prednisone with ultralow-dose aspirin. The prednisone has immunosuppressive effects, and the aspirin helps prevent thromboembolism, which may occur in these patients; thromboembolic sequelae in particular play a role in the morbidity and mortality of patients with immune-mediated hemolytic anemia. Aspirin can cause gastrointestinal (GI) ulcers in dogs, but ultralow dosages (0.5 mg/kg/day) are usually considered safe. A recent study in the Journal of Veterinary Internal Medicine investigated whether combining prednisone with ultralow-dose aspirin might also be safe in healthy dogs. The researchers did not perform the study in sick animals because it would be difficult to determine whether it was the drugs or the disease itself that was causing GI effects.

The researchers observed 18 healthy dogs that were between the ages of 12 and 24 months and weighed between 12.2 and 17.9 kg every eight hours for 10 days before administering the drugs or placebos. They noted the number of bowel movements as well as any GI signs. The dogs also underwent a gastroduodenoscopic examination seven days before therapy was instituted to detect any pre-existing lesions on the GI mucosa and obtain a baseline appearance. Once therapy was initiated, the dogs were separated into three groups-those receiving only prednisone (2.2 mg/kg/day), those receiving prednisone (2.2 mg/kg/day) and ultralow-dose aspirin (0.5 mg/kg/day), and a control group that received only placebos. The researchers were blinded as to which group each dog was in. The dogs received these medications for 27 days, and the researchers continued to observe the dogs every eight hours and note any GI signs and the number of bowel movements. The dogs underwent additional gastroduodenoscopic examinations five, 14, and 27 days after drug or placebo administration began.

In terms of GI signs, no significant difference was found among any of the groups for vomiting or diarrhea, and no dogs showed signs of dehydration, lethargy, or inappetence after 27 days of drug administration. The findings from the gastroduodenoscopic examinations were also not significantly different. However, about one week after the drug administration began, the dogs that received prednisone and aspirin-two dogs, in particular-did have a significant increase in the number of episodes of diarrhea compared with before treatment initiation. The diarrhea was mild and resolved within five days of halting the aspirin treatment and decreasing the prednisone dose, indicating that the drugs were a factor in the diarrhea development. But since the diarrhea was mild and the gastroduodenal lesion scores didn't differ among groups, the researchers thought, overall, that a combination of prednisone and ultralow-dose aspirin is safe in healthy adult dogs for at least 27 days. They did caution the usage of this regimen in older sick dogs because the diarrhea may worsen with age or illness, and they suggest that clinical studies in such dogs are needed in order to further evaluate adverse effects associated with this drug combination.

Graham AH, Leib MS. Effects of prednisone alone or prednisone with ultralow-dose aspirin on the gastroduodenal mucosa of healthy dogs. J Vet Intern Med 2009;23(3):482-487.

Link to abstract: http://www3.interscience.wiley.com/journal/122343868/abstract