Dear patricia,
Asacol is a delayed release tablet for oral administration of mesalamine, a 5-ASA compound. The tablets are coated with an acrylic-based resin that delays release until the terminal ileum and colon. Consequently, only a small amount of the 5-ASA is absorbed, approximately 25% of the administered dosage.
Adverse drug effects can be categorized as idiosyncratic (i.e. does not occur in everybody) or predictable (i.e.occur in a large number of recipients and is dose dependent). Asacol has been shown to cause a low platelet count. This effect is very rare and is considered idiosyncratic.
ASA can cause an impairment in platelet function that is a predictable response that is dose related. It is conceivable that there could be an effect on platelet aggregation with Asacol but it would be unusual, given the small amount of drug that is absorbed. I could not find any references to platelet aggregation effects during a review of the literature for the last 3 years.