Is my little girl going to be ok after heartworm treatment

I took my dog to the vet to get her heartworm treatment on the 2nd and she's been fine, just a little slow. Now today she's started caughing up alot of phlem and wont even get up to go potty she just lays there and goes where she's laying unless I go physically pull her out of her kennel. Then she gets up and walks. Is this to be expected after the treatment. She ate today and is drinking water ok. I'm just really worried about her. The Vet isn't open until Monday and gave me no emergency number.

Patti