My dog started drug therapy today for multiple parasites. He is acting funny, please help!?

this is not a reaction from the antibiotic or steroid but it could be a normal reaction from the flea pill (comfortis). when was the comfortis given? usually about 30 minutes to an hour after its given, if the animal has fleas, they will go through an intense itching/ chewing session (presumably from the fleas dying and rapidly biting). if it continues, call your vet just to make sure.