anxiety

I have a 10 yr old female cockapoo when it is getting ready to storm and is storming she shakes and pants something terrible, sometimes I worry she'll give herself a heart attack. What can I do or is there some kind of medicine I can give her to help her through this. My son has a 6 yr old 1/2 lab 1/2 dalmation, which had lived with his dad for a year, as far as I can figure he left her alone quite often, now that she has been back with us for 3 years, we have to leave catoons on for her if we leave or she will tear up stuff and she has spells where she whines and mopes around constantly when were home. When I had her she only did that once and it was when my son was gone for a week and I even had him talk to her on the phone and she would be better for a while. Is there anything I can do for her. She appears to be depressed so often. Thank you