BENTONVILLE, Ark. — Walmart and Humana Inc. will offer the least expensive nationwide Medicare Part D prescription plan.

Called the Humana Walmart-Preferred Rx Plan, the prescription program will be offered in all 50 states and the District of Columbia at a monthly premium of $14.80.

Medicare recipients can sign up for the plan from November 15 until the end of the year. Executives say consumers can learn more about the plan by visiting one of the informational kiosks being put in more than 3,000 Walmart stores across the country. The kiosks will be staffed by Humana personnel. Information is also available via phone or on the Walmart and Humana web sites.

According to Centers for Medicare and Medicaid Services data cited by company executives, the average cost of a Part D plan next year is expected to be between $37 and $38 per month.

Comparing the cost of their co-branded plan with the average cost for a Part D prescription drug plan in 2010, Walmart and Humana executives estimate that the co-branded drug plan will save a typical Medicare Part D beneficiary more than $450 on plan premiums, medication co-payments and cost shares next year.

“We know every dollar counts, especially when you live on a fixed income,” Walmart Health and Wellness division president Dr. John Agwunobi says. “We believe no one should have to choose between buying their groceries or their medications.”

Agwunobi and William Fleming, head of Humana’s pharmacy unit, stress that financial health is a critical part of a person’s well-being.

“People are more likely to take the medications prescribed for them when they can afford those medications,” says Fleming, vice president of Humana Pharmacy Solutions. “Adhering to prescription-drug regimens can enable people to prevent future illness.”

The co-branded prescription plan will offer co-payments as low as $2 when plan members fill their prescriptions in one of the pharmacies the retailer operates in its Walmart, Neighborhood Market and Sam’s Club outlets.

Because the number of people enrolled in a stand-alone Part D plan is expected to reach 26 million by 2015 (up from the current 18 million) and because seniors generate a third of all prescriptions filled in the United States, the co-branded plan is likely to mean a flood of new patients into Walmart stores.

Agwunobi says the company’s pharmacies can handle the increased traffic. “We have invested in building up our pharmacies, making sure we have the right staff in the right place at the right time,” he says.

Meanwhile, co-payments for generic prescriptions filled using Humana’s mail-order service will be even lower. Patients who opt to fill generic prescriptions through Humana’s RightSource home-delivery prescription service will have no co-pay, the companies say.

Over the past few years generics have come to be an integral part of Walmart’s pharmacy operation.

During a conference call to discuss the details of the co-branded Medicare prescription drug program, Agwunobi noted that since 2006, when the company began offering its 30-day generic prescriptions for just $4 apiece, the program has saved patients across the country more than $3.4 billion.