help! my dad went crazy!

[chuckrocks]

my sister is checking the med websites, i thought i could get some input from my community.
he's 64, a retired pipe fitter, and lives in hahira ga. we're on the way there for xmas tonite. he got a case of what was thought as an infection in his lungs, so they dosed him with telethromicine(sp?) 10 the first day, then down by 2 per day until 1 the last day. then gave him zertec for an allergy reaction(he does yard work for my g-ma's church)and prednizone for a rash he had most likely from the yard work.
it all started with a fever. about 102. mom gave him some tylenol and he felt better. then came the walking pneumonia. he got on the antibiotics and was sleeping most of the day. thats when he started pacing the house like he was lost. my mom asked him what his son's name was, and he just stared at her. she took him to the doc, and he had him count the buttons on my mom's blouse (10) he got up to 36. they have done a cat scan, he has no abnormal blood counts, he hasn't had a stroke, and they say this is too sudden to be Alzheimer's. we are all dumbfounded, including the doctors.
if you know anything or have been through this, i'd appreciate a little guidance. i'm sick to death, my last memory of HIS father was a curled up 80lb bag of bones in a hospital. Alzheimer's is not new to his family.
edit: thanks everyone for your input and thoughts. i've got a host of questions for the doctors tomorrow. i also have a ten hour drive starting in about a half hour. talk to ya'll from GA!
thanks again!