Medications do they differ?

What kinds of medicines are available to help patients? Are they for the disease itself or the effects of the disease?

There are several drugs currently on the market to help alleviate symptoms of the disease. Some of which include cholinesterase inhibitors which are prescribed to those patients suffering from mild to moderate alzheimer’s; rivastigmine or galantamine for the early stages which on the market may be known as Razadyne or Exelon. For the mid to late stages FDA has approved Namenda (memantine) and Donezepil. The main effect of the drugs in prescribed in the later stages of Alzheimer’s is to delay the progression of symptoms. Non of these will prevent or stop the effects of alzheimer’s but such medications are in testing.

There are hundreds of other medications that can be prescribed to control other symptoms such as sleeplessness, agitation, anxiety, depression, wandering, etc.
http://www.nia.nih.gov/alzheimers/publication/alzheimers-disease-medications-fact-sheet

Another aspect I would like to research further is are these drugs being prescribed for any other medical problems? Or were they strictly developed for the disease.