There are products that I have personally reported to Ebay about misleading heartworm treatment and preventative products being sold on Ebay.  These products have absolutely no effect on heartworms and one even lists alcohol (another ebay violation) as an active ingredient.  Please don't be fooled into believing these products are going to help your pets.  Be forewarned, the only effective FDA approved company guaranteed heartworm preventative products are from your state licensed veterinarian.