I’m almost positve you don’t have a waiting period- caracream is just another ‘form’- it’s still prevacid-if the dose is different (higher) then maybe it will take a few days for the new dose to take affect
zantac needs to be spaced apart from PPIs (prevacid, prilosec, nexium, protonix) regardless of their ‘form’ (compound, capsule, solutab, packet)- we were told to space a PPi & zantac 2 hours apart and we were fine with that, but the majority of parents who post here report that their drs say to wait 4 or 5 hours…
we stayed on zantac until it was apparent that it wasn’t necessary anymore…then we used it ‘as needed’
HTH (hope this helps)