Express Scripts Inc said on Thursday it was moving forward successfully without Walgreen Co in its pharmacy network, citing wide support from clients.

Chief Executive Officer George Paz said the pharmacy benefits manager remained open to talking with Walgreen, but it has got to be in the best interest of our shareholders and patients.

Walgreen, the largest U.S. drugstore chain, stopped filling prescriptions for patients in the Express Scripts network as of January 1 after the companies failed to come to terms on a new contract.

Our clients are very supportive, Paz told analysts on a conference call to discuss the company's fourth-quarter results. Our phones aren't ringing, people aren't concerned, our clients aren't upset, so this truly has been a good move for us.

Express Scripts shares rose 4 percent in morning trading on Thursday.

The company also said it still expects to close its $29 billion acquisition of rival Medco Health Solutions Inc in the first half of the year. Medco shares were up 3.7 percent.

Paz said Walgreen has not shown why they should be paid more than other pharmacies.

Many of the things that they are offering in the pharmacy are being offered by many others out there, he said. So I don't see them as differentiated, and I just can't with a good conscience pay them a significant premium for something that everyone else is doing and doing it just as well.

Express Scripts beefed up its call centers to handle questions from consumers about the Walgreen exit. Those costs, plus costs tied to its anticipated acquisition of Medco and some unexpected taxes, led Express Scripts to slightly miss analysts' estimates for fourth-quarter profit.

But the company reported an increase in prescription claims for the first time in 2011, noted BMO Capital Markets analyst Dave Shove.

The U.S. Federal Trade Commission is reviewing the Express-Medco deal, which would create the largest U.S. company for managing pharmacy benefits for employers and other clients.

The companies have maintained that their merger will create an entity with more clout that can drive down prescription costs.

We believe that this acquisition speaks to what this country needs more than anything, which is a reduction in the cost of healthcare, Paz said on the call.

(Reporting By Lewis Krauskopf; editing by John Wallace)