I have tried it at different times (it did not work).
I had to take my big tabby cat Silver to the vet. He was moaning up a storm and very upset.
The vet was obviously afraid of him and she whipped out a can of Feliway and began spraying it around the room. That scared poor Silver even more and the moaning got louder and the vet became terrified of him (he is a very big tomcat).
After that, I put him in the carrier and said, "Come on Silver, we are going home now and we won't be coming back here again". And so we did!
All of this said, I don't think it does any good. I'd tried it on my old sofa to try to get the cats to not claw it and that did not do any good either.
I guess you could give it a try but I would not spend a whole lot of money on it.
As for calming cats down, I have no good tips other than to remove them from the situation that is stressing them out. 
I hope this helps and forget about these "treat" things they sell called "Composure" or some such thing is the name. Bought and tried those too and nope!
Best of luck!
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