I too have had brain surgery and I can tell you it is very difficult. There are so many things that can happen to your body from having brain surgery. Just think.... your brain controls everything in your body, so if you have surgery on it, it can affect anything in your body. My appetite and my problems with urination have never been the same since my surgery and it was 6 years ago! I know what your father is going through. The problems with him urinating so frequently at night is more than likely from his brain surgery, but you should still tell him to go to the doctor to have his prostate checked and to make sure that there are no other issues. I am pretty sure that his problems with his bladder are caused by the surgery, but you should have it checked out to make sure. If it is from the surgery, there are some things that you can tell your father to do to help lessen the severity of the frequent urination. Tell your dad to try holding his bladder during the day when he feels that he needs to go pee. If he can practice holding his urine during the day, it will help strengthen the bladder. Strengthening the bladder will help him at night because it will help him be able to hold his pee longer at night and then he won't get woken up as much because of needing to go pee. Also, tell him to stop drinking liquids 4-5 hours before bed times. Tell him to try his best not to drink any more than he has to during that time before bed. This will help because his body will be filtering all of the liquid in him during that time period, and then he can hopefully empty the bladder before he goes to sleep. Then since he won't be drinking anymore liquids before bed, he shouldn't have to get up as much throughout the night to pee. I know what you and your dad are going through, brain surgery is hard. I hope that my post helps you out in some way. If you need anyone to talk to, I am here. I hope that your father is doing better.
how old is your father? i would definitely have him consult a physician for the urination.
i've taken ambien and don't consider myself addicted, but i do know that some sleeping pills ar ehabit forming.
Has he tried Melatonin? You can buy it at your local drug store and is a chemical that your brain naturally produces to help you sleep (from what I know; you may want to do more research). When i take Melatonin, i get a good's nights rest and melatonin is non-habit forming and from what i know, doesn't have any negative side effects.