I've been ordering from Budgetpetcare for years for heartworm and flea meds. I now do auto-shipments for 6 or 12 months' supply. The prices are the lowest I've found, and they often have special discounts. Customer service has been good, eg. When a shipment was delayed once. Really prompt responses via email. There is a dollar-plus fee for customs or what-have-you since the products come from overseas.