The side effects of the drug include poor appetite, lethargy, diarrhea, dyspnea, azotemia, weakness, and ataxia. Therefore the
symptoms could be connected. I would absolutely take your dog
to see the
vet as soon as possible, as this is quite a complex drug which must only be given to dogs with properly diagnosed heart fallure. It should not be given to dogs under 6 months of age, to pregnant or lactating dogs and certain forms of cardiac disease.