I am POA. My father has been taking money out of his account every 2-3 days ($300 or more) and has been giving it to his son. I have a feeling my brother is doing much worse as on a background check I did, there was an Alias listed which was my father's name. How can I protect my father?
I also would get credit reports, move to put security freezes on his credit files with the 3 credit bureaus, speak to bank officers about putting restrictions on his accounts, if necessary transferring money out so he can't access cash to give to your brother. He may encounter overdraft fees, but at least you'd be securing the accounts against further withdrawals.
I do suspect though that banks aren't going to become involved in blocking your father's access to his funds. You may have to close the accounts and open new ones specifically as a DPOA.
If he has investment accounts, notify them first by phone to find out what preventive action is available, then confirm it in writing. You don't want to be accused later of not taking all the preventive steps you can.
The biggest problem I see though is that your father is apparently giving your brother cash, which suggests to me that his addiction isn't to prescription pills but rather to street drugs. In this case, I really think it's appropriate to contact law enforcement. Maybe getting your brother in jail and out of the picture is what's necessary.
I suspect also that this isn't something new but has been going on for some time. In that case, your brother may have prior offenses.
In addition, I'd investigate what kind of drug rehab programs are available for your brother.
Although you didn't raise it, I can't help being concerned after reading that your father is living at home. I'm wondering if your brother is capable of violence if he's cut off and if your father's welfare is in danger. If so, I would certainly raise that with the police as well.
Law enforcement might also have other suggestions to protect your father's financial assets from the dealers.