Hello, welcome to JustAnswer! I am a Veterinarian and will help you right away!
First, I am glad you decided to take on this challenge with Karina and her anxiety. I understand that it is hard to do charity work and still make ends meet. It sounds like you are doing a good job though, and care about pets. SO, I am going to help you.
Separation anxiety can be very very very difficult to treat. It is complicated.
I will give you a few tips, you may have already heard but here they are.
Some of these are tips I give to owners to work with the pet. This is an essential part of the treatment, EVEN if you are not the eventual owner of this rescue dog.
I will also discuss medications I feel are helpful towards the end ok? You will need to get them from a Vet though. The stuff over the counter helps sometimes, but almost always you will need prescription strength meds AND behavior modification to help this pet.
One way to reduce the stress is to not show your pet when you are getting ready to leave. What I mean by this is when you get ready to go, grab your keys, and head out the door without any fuss. The longer you take to leave, the more time your pet is anxious. Also, if you talk to them and try to calm them it doesn't work. They aren't thinking "Well, I am pretty terrified that they are leaving me again, but at least they are telling me this time it will be ok. So that helps" No. They are thinking "I KNOW THEY ARE LEAVING ! I AM GOING TO BE LOST FROM THE PACK AND I AM GOING TO STARVE TO DEATH HERE BY MYSELF!"
Seriously though, the anxiety they feel is a terrifying level. They are so scared to be left behind they might try to dig under a door until they have torn off their nails. Not all cases are that bad, but some certainly are.
So, what you can do is decondition the pet to you leaving as well. Get up, get your keys, walk to the door, then come back and sit on the couch. Then... do .... nothing.
When the pet calms down, and is sitting calmly, give a reward. Don't forget to reward the calm behavior. This is the behavior we want. Do this once a day for several weeks, until it seems like the pet is not as tense or hopefully doesn't even respond when you go and get the keys. This is the first step, and when that happens you know you have made progress.
Also, this is what you HAVE to do. When you are leaving for real, completely ignore the pet. Don't say or do ANYTHING. Do NOT give any treats, or talk differently to soothe them. These, like I said, are all triggers that this is the REAL THING. You are Definitely leaving this time. Also, do this when you come home too. When your pet is jumping up and so happy to see you, just ignore him. Go and walk over and sit down on the couch. Wait for him to calm down. Then give him a treat. This doesn't mean you have to have a boring dog that doesn't great you. Just teach him that it is ok to be alone, and don't reward him for behaving badly when you get back home. Likely he has been barking, and tearing things up, and when you get home if you pet him and give him attention, you reinforce it.
For some pets the TV helps. For others it causes more stress. Let's say you leave with a nice cartoon on with soothing sounds and voices, and before you come back it changes to the evening news with a live shootout and car chase scenes!!!!! Yeah, bad idea. They make DVD's for pets too. But again, some dogs have no interest in the flashing pictures noisy machine. Indeed some pets can't see 2D images very well at all, and just perceive it is as movement.
It helps to have something to do during the day like a kong treat filled with peanut butter and then frozen. This will take HOURS to get bored. Lots of toys help.
In some pets the fear is soooo much that we use a medication called Clomicalm. It doesn't have to be given for life always. But, it does help some dogs adjust while you are doing the other treatment I have listed for your friend. Ok?
Here is a link on Separation Anxiety that I find very helpful. The Clomicalm information is at the bottom of the screen. You will have to get that at your Vet. BUT, beware that this is NOT the solution. It will take hard work on your part AND the medication to get your pet back to normal, and give them the life you want them to have without fear. Click here for more info and scroll down to the treatment portion
I think you are referring to xylazine. This isn't used much for anxiety anymore in dogs. Too many side effects.
I want to share this link with you from the ASPCA. It lists MANY types of behavioral problems and treatments for dogs. And it is good resource that will help you in the future as well for your rescue dogs, ok??? This link talks about many different medications and options that have been tried.(click this link and bookmark it for later use)
If that doesn't help at all:
Keep in mind again, some behaviors are very very hard to treat.
If a person changes their behavior quite suddenly we suspect something is wrong with them. If they are aware of the changes but unable to control them, they often seek medical help in the form of a Doctor that treats behavior problems. In humans that's a Psychiatrist, but in animals we refer to Veterinary Behaviorists.
This is a true specialty in Veterinary Medicine and these Doctors can help you diagnose the problem faster and get you to an acceptable answer faster as well. It is almost IMPOSSIBLE to give any help online with behavior. It is best dealt with a one on one approach of treatment and behavior modification.
I hope you understand.
The American College of Veterinary Behaviorists recommends the advice on finding an acceptable trainer How to select a trainer link
This link will help you find a Board Certified Behaviorist in your area Click here
I hope you accept my answer. I don't think you need to join and become a member to accept a one time answer though. At any rate, I hope my answers help you now and in the future anyway! Good luck with your rescue! :)