How do I know if my 81-year-old father is on too many (possibly unnecessary) medications?

Doctors ore the worst people to ask. Most practice "conveyor belt" medicine and want to spend as little time as necessary with patients. Going over meds takes much too long.
I have had better luck with a good pharmacist. If you schedule an appt. they will help you sift through the meds and tell you what things interact or may be redundant. Also, the Physician's Asst. at Mom's doc's office is quite good and they have more time to deal with "details." We also have a naturopathic pharmacy here and they are really knowledgable about all medications and have given us great advice.
It seems that whenever Mom goes to a new doc or specialist, they do not want to change what the previous doctor recommended but then they add to their meds. Also, Western medicine teaches them only two modes: pills and surgery. I finally got Mom down to 3 regular medications.
good luck