OCTASA (mesazaline) side effects

Hi,

 I started taking 3 tablets a day of OCTASA and nine days in developed terrible stomach cramps and headaches. After a couple of days this subsided and was replaced with chest pains when breathing. I went into hospital last week and was discharged yesterday with no conclusive results.I started seeing symptoms of UC for 3 months prior to my diagnosis with none of the above issues so everything as far as I am concerned pointed to the side effects of the pills. What I had are all listed on the sheet albeit at the rare end but it seems very coincidental all the same.  

The hospital have now put me on a single tablet of Asocol as a replacement. 

Has anyone else suffered acute side effects?