LEWISTON – The corner of East Avenue and Sabattus Street apparently holds a prescription for success.

How else to explain the decision of drugstore giant CVS to build a new store directly across from an existing Rite Aid? The new CVS received approval from city planners last month and if all goes according to plan, will open next spring.

The corner, which has also piqued interest from Walgreen’s in the old Cottle’s location, could become a local hot spot in the battle for a share of the country’s $250 billion prescription drug sales – a market that will only continue to grow as Americans age. Currently, chain pharmacies fill about 40 percent of those orders, outpacing online, mass merchant and supermarket pharmacies, according to the National Association of Chain Drug Stores.

“It’s very simple,” said Laura Miller, economist for NACDS. “Stores are where the people are. That’s the bottom line.”

The new $1.2 million CVS store will offer drive-through services and 13,228 square feet of retail space – about 10 percent bigger than its existing store at East Avenue and Lisbon Street, which is expected to remain open.

Site locators for chain drugstores are very sophisticated and use complex demographic formulas to decide where they go next, Miller said. But an industry rule of thumb is one drug store for every 5,000 to 10,000 people. There are 13 pharmacies in the greater Lewiston-Auburn area, which has a population of about 106,000, indicating some room for growth.

“Next they look for convenience,” said Miller, which means a well-traveled commuter route with properly zoned space. In 2005, the Sabattus Street/East Avenue intersection averaged 11,040 trips per day – about half the daily traffic load counted between exits 75 and 80 on the Maine Turnpike.

“They try to get close to the most traveled routes and as close as possible to the center of the population they’re trying to reach,” Miller said. “Obviously the answers can be the same. The only difference is what company’s name is on top of the store.”

That population is expanding as people get older and take more medications. According to an NACDS study, between 47 and 55 percent of people 35 and under take at least one prescription medicine a day. For people ages 65 and older, that percentage rises to 91 percent.

“As the population gets older, the trend clearly goes up,” Miller said.

About 40 million people will be 65 or older by 2010, according to the U.S Census.

Although CVS officials declined to comment, its 2006 annual report offers some insight behind its expansion plans. It projects that U.S. pharmacy sales are going to grow at an annual rate of 5 to 8 percent for the foreseeable future.

“An aging population, rising use of generic drugs, the Medicare Part D prescription drug benefit, and new discoveries are some of the key factors driving the greater demand for pharmaceuticals,” reads a portion of the report. The company also wants to be poised to capitalize on the rash of branded drugs that will lose their patents over the next five years – about $50 billion worth, the report said. Generics give retailers a higher profit margin than brand-name drugs.

CVS added 2,000 new locations between 2003 and 2006. Plans are to add 275 new or relocated stores this year.

Others will likely do the same, said Miller, citing robust sales. In 1995, there were just over 2 billion prescriptions filled in the U.S. In 2005, that rose to 3.3 billion.

“That’s a pretty big increase in 10 years,” Miller said. “And the baby boomers haven’t even turned 65 yet.”