Hi!
I also take Pentasa 4g per day.
Are your tablets 500mg each? I was on those, but then changed to 1gram tablets, which I believe are a new dose, as many chemists didn't have them and my local one ordered them in for me.
I had real problems with the flat round 500mg pills, but the 1gram ones, even though they are bigger, are much easier to swallow with a swig of water as they are oval shaped.
Also, it is OK to break the tablets as long as they are not crushed. They are easily broken down in water and, as long as the actual granules are not broken they will work fine. My friend is a pharmacist and she confirmed that this is OK. The packet actually states that you can break them but not crush them. You will have to get your GP to specify the dose of tablet on your prescription, as the pharmacist has to dispense what is stated exactly on it and cannot substitute an equivalent one.
If you have no luck with the 1gram tablets, or if they don't fit with your dosage, try asking for the granule sachets.
Good luck.