It appears to be a brand of mesalamine (aka mesalazine) which is a common IBD med. Mesalamine is available under a ton of different names, like Asacol and Pentasa...the real difference between them is the amount of mesalamine and the controlled release mechanisms. The medication is released from the pill at a certain time after being taken so that it treats a specific region of intestines. I think the Octasa brand name is only available in the UK though. Hope that made sense!