Thanks for res[ponding. The drug that I have been prescribed in the UK is Balsalazide, under the brand name 'Colazide'. The Farmacia in Spain tells me that neither the drug (Balsalazide) is not available in Spain under any brand name.
However, I have discovered through the internet that there is an alternative, which is called Mesalazine. Perhaps you cold confirm.
Balsalazide is a precursor to mesalazine. Not the same thing but you can say balsalazide can release mesalazine beyond the small gut, it has this advantage over it. So if the large gut is affected by the inflammatory bowel disease or colitis, then balsalazide will be a better drug, but mesalazine can be used none the less. I would also advise you to check with the local pharmacy about the dose and get a gastroenterologist's opinion on the dose and substitution of the drug.