They are just different types of reflux medications. The zantac works quicker and on the acid that is there, wheras the losec works to stop the acid actually being produced. It can take a good two weeks for it to work and dosing is as hard as the zantac.

They do eventually get used to the zantac, Parker used to fight it so bad, so I know exactly what you are going through, but hopefully he won't be like that for very long.