Petco.com is currently offering a four month supply of K9 Advantix from 48.99-51.99! You can also get free shipping on orders over $45.00 by entering springsave at checkout. Shop through ebates and earn 6% cash back on your order. You can also go in through an ebates link that would give you 10 dollars off a $60.00 purchase. If you have other items to order this could be a pretty good deal.
If you don't have an ebate account sign up today. Not only do you earn cash back by shopping online, you can earn extra money through referrals. You can receive your money through paypal or a check every three months. I was amazed at how quick and easy it was to use!