I'm having serious problems with muscle weakness and recently saw a physiotherapist for an assessment. She couldn't explain what has caused it, as I am generally an active person, haven't had any injuries that might be responsible either. It never occurred to me till just now that it could be caused by mesalazine, but I was just googling side effects for another purpose and found that mesalazine can actually cause muscle weakness. I'd be interested to know whether anyone else has had this problem?