My father has alzheimers. Aricept and namenda (memantine) had worked well-but not so well lately. Whats next?

Modest meds. The memory enhancing agents for alz are not cures and only modest control measures. Usually benefits last only a few years. Two other choices might be Exelon patch or galantamine, (galantamine hydrobromide) but you might want to first go to Aricept 23, if not tried yet.