It's scary when something like this happens, and on a weekend (of course it happens on a weekend! Just be glad it isn't a 3 day Monday holiday weekend!)

Only you can decide if she can wait for the vet office to open again tomorrow, or if she needs to see the ER vet.

The ER hospital near me would answer this question for me over the phone, but I don't know if all of them will do this: "My dog started panting heavily after Quadritop. My vet told me to stop it, which I have done. Now, 7 hours later, she is still panting heavily. How long does it take for the side effect to wear off?" So you may want to give them a call, see if you can get some info that way.

Where do you live? Is it hot / humid there today? Do you have a/c? This could also account for the panting. Just a thought.