GREAT !! Thanks for posting back, you never know another dog on here might do the same thing.
I called the emergency vet and they said just to monitor him that he should be ok and lucky he is.
Oh, my...I do hope by now that you have called the emergency vet- they can at least tell you if you have anything to worry about. It's too late to do this, but in some cases you can induse vomiting by giving 1 tablespoon of Hydrogen Prioxide, I have three dogs and I have had issues like yours. The Guaifensin I don't think will be an issue, and the other might speed up his heart- that is the one I would really want to know about.
Please call the emergency vet right now and ask them, they will tell you if you need to bring him in. Please post an update. I hope all will be fine.