Vetafarm Products offers veterinarian approved medications for all animals. All Vetafarm's products are regulated by the Australian Government which assures the highest of quality standards and consistency in the products they produce. Heartworm prevention is a critical part of your dog's care. Using a cheap formula may not have any effect on the worms transmitted by mosquitoes to your pet and could lead to development of heartworm disease that might require expensive and painful treatment to cure. For more information call us on (661) 295-6700 or you can visit our site: http://www.vetafarmproducts.com