It's stands for Costco Member Prescription program. As long as you have a costco card, it's free. It doesn't matter if you carry insurance on yourself..since you'd be filling the prescription under your pet. It's free to all members and their dependents who do not have insurance (animals don't carry prescription coverage) or have insurance and their insurance doesn't pay for a certain drug. Keep in mind, Costco only carries drugs for humans. So, for instance, you wouldn't be able to get Rimadyl there.
