I don't know much about that product, but I wouldn't use a drug(or herb) as a substitute for training. Granted, some dogs are just going to be freaky about their master leaving, but training can make it better, if not totally eliminate the problem.
Dogs pick up on things that you do, which let them know what's about to happen. My Lab knows that when I put my shoes on, it means time for a walk. If I grab my keys also, he knows I'm leaving without him. If your dog gets worked up when he notices you're about to leave, start doing those things without leaving. Put on your shoes and stay at the house as a test. Desensitize him to the triggers(over time).
I had a Dacshund years ago that would chew everything in the house when I left(this was before crate training was popular). I started leaving for a few seconds, then come back inside. I kept doing this until she stopped going crazy and barking. Then I increased the time away from her without barking. Eventually, I could stay outside for 10, 20, 30 minutes before she would make any noise. Eventually I could stay out most of the day, because she got the idea i was coming back. Successive approximation.
It doesn't happen in one day. It's something that has to be focused on, but the reward is no more torn up couches and shoes.
Sorry for the unsolicited advice, but I wouldn't trust anything that's supposed to calm my dog without training.
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