My vet wanted to deworm my indoor cats twice a year as a preventive measure. I questioned this, did my research, and finally agreed to a once a year treatment. I should have done more research on the mediation, Profender. From the time they were given the treatment until I got them home and let them out of their carriers was less than 30 minutes. My 2-year-old cat came out hissing and spitting and attacked my 10-year-old cat. She would not be in the same room with him, nor would she eat. She began vomiting and crying. Then my older cat began attacking her and the fur was flying everywhere. As the behavioral issues worsened I spoke to my vet who said to let her know the next day if there was an improvement. By the netx day bald patches appeared on my older cat and he began pulling his own fur out, sometimes with the skin still attached. In the meantime I had washed both of them with mild soap and water where the Profender had been applied and put antibiotic ointment on the bald spots, which now were broekn skin. Unfortunately, while I had researched the deworming recommendation I had not researched the Profender. I was horrified to find all the sites like this where people were reporting the same side effects. I felt like a negligent pet guardian and have lost confidence in my vet. Do not allow anyone to talk you into using Profender. If your cat has worms there are other products that can be used for treatment. This medication is dangerous and should be taken off the market!