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218 LONG-TERM THERAPY WITH 5-ASA AND PLATELET DYSFUNCTION C Teshima1, F Habal2 AIMS: Sulfasalazine and 5-aminosalicylic acid (5-ASA) are mainstays of therapy for mild to moderate Inflammatory Bowel Disease (IBD). It is not uncommon for IBD patients to be advised to discontinue taking 5-ASA prior to surgery or invasive procedures for fear of increased bleeding complications out of the assumption that 5-ASA inhibits platelets due to its molecular similarity to acetylsalicylic acid. However, although one of its many mechanisms of action may include partial inhibition of cyclooxygenase, 5-ASA has not been shown to affect platelet aggregation, the best marker of platelet function. Since there is only a single study done in 1987 with 6 patients using less sensitive tests than that available today, we undertook to examine the effect of 5-ASA on platelet aggregation.
1University of Alberta, Edmonton, Alberta; 2University of Toronto, Toronto, Ontario
METHODS: 10 patients with IBD in remission on stable doses of 5-ASA for at least 1 year were enrolled. Patients were excluded for thrombocytopenia, a history of a bleeding diathesis, or for taking Aspirin, Clopidogrel or any NSAID. Platelet function was assessed using the Platelet Function Analyzer (PFA)-100, a computerized instrument that provides an in vitro measurement of bleeding time. The platelet photodensitometry assay used in the previous study was also repeated for historical comparison. A control group of 10 patients without IBD on daily Aspirin was included. Urine was tested for the presence of urinary salicylates to confirm medication compliance. The tests of platelet function were then compared to established normal values.
RESULTS: The 10 study patients on 5-ASA had PFA-100 bleeding times ranging from 78 to 179 seconds with a mean of 113.4 seconds (95% CI 95.5-133.1), with normal <193 seconds. The 10 control patients on Aspirin had PFA-100 bleeding times ranging from 246 to 300 seconds with a mean of 277.9 seconds (95% CI 262.3-293.6). The results of patients on 5-ASA were significantly different from both the upper limit of the established normal range (p <=0.002) and from the results of patients on Aspirin (p <=0.0019). All study patients had urine studies positive for salicylates, verifying compliance and absorption of the 5-ASA medication.
CONCLUSION: Patients with IBD on long-term therapy with at least 3g/day of 5-ASA medications have normal tests of platelet function and are at no increased risk of bleeding from platelet inhibition. This clearly differs from the inhibitory effect on platelet aggregation caused by daily Aspirin.