Can anyone give me advice on the best medication for my partner age 79 years
who is suffering from loss of memory,compulsive obsessive disorder,checking
everything all day and most of the night has a memory span of about 20
seconds before I have to repeat everything again, and again ...

I've been finding that since taking mirtazepine, I wake up every
morning with a totally dry mouth. This is more than just an
inconvenience, as I believe lack of saliva during sleep can promote
tooth decay.

J Pediatr Orthop. 1997 May-Jun;17(3):397-401.  Related Articles, Links  
Neonatal gangrene of the extremities.
Letts M, Blastorah B, al-Azzam S.
Department of Surgery, Children's Hospital of Eastern Ontario, Ottawa, Canada.