Hi, all! I order Maggie's flea meds through the internet -- they are so much cheaper than at the vet. Now I need to switch Maggie to Interceptor for heartworm prevention -- due to her extreme sensitivity to ivermectin, I do not want to even give her the tiny bit in Heartgard. I know my vet is concerned about quality control with on-line meds although he will write me a prescription if I ask. I found great prices on Interceptor at both Drs. Foster & Smith and Pet Shed. Your thoughts?