A patient is identified as having stage 2 Alzheimer's disease and elects to take donepezil (Aricept). The patient asks the primary care nurse practitioner (NP) how long the medication will be needed. The NP should tell the patient that donepezil must be taken:

a- until symptoms improve.

b- indefinitely because it is not curative.

c- for 24 weeks, which is when cognitive function improves in most patients.

d- until symptoms worsen, when a switch to memantine (Namenda) will be needed.