A lady I have chemo with (also on topo), mixes the
Miralax in warm prune juice and says it works great. You can also take stool softeners with the
Miralax. Hopefully, the chemo will take care of the tumors on/by your Mom's colon.
IF your Mom goes on iron, there is a new pill "HEMAX" (an Rx) that is a combo of Vitamin C, Iron, and stool softener. You need to take iron with Vitamin C for good absorption.
Good luck .. don't know anything about Gemzar ..