It's not that the actions differ at all, simply this compound hits an extra receptor for glucagon along with the others that the similar medication does. I don't think there would be problems in theory, yet I found it necessary to keep taking the original pair during the process of slowly raising the amount of the new one and lowering the previous, finally stopping after a few weeks span. I picked a time with fewer demands just in case the digestive problem flared up again.
I've had IBS for more than 40 years where breakfast always sent me to the bathroom within an hour. It vanished completely the first day on Tirz and bowel movements became normal. The slowed emptying on Tirz is probably why, but I'm wondering if the IBS would come back on Reta because its mechanisms differ. Anyone have experience with that?