When Cash got Lyme disease he was given this and he got better within a matter of days. I never noticed any side affects whatsoever except that he was better. When my pup Cap'n had to go to the vet for bloody stool he was given it for an intestinal infection due to a really bad worm infestation. Poor little guy. The day I picked him up he was given albon, a week later he was given albon again, then he went through 3 days of panacur, and STILL had worms. I wanted to slap the lady that bred him. Anyway I noticed with him he was really sluggish, tired, and had diarhhea but I assumed the majority of that was due to the worms.