The insurance company is probably responding to the Lipitor "co-pay" situation. Once the generic forms were given the go ahead, Pfizer, the maker of Lipitor tried lowering its prices, but was unable to compete with the $4 generics. So they devised the "$4 dollar co-pay". But the lower price comes with conditions that may be what has caused your insurer to balk:
http://myhealthcafe.com/pfizer-offer...ood-to-be-true