Updated from 11:58 a.m. EST

Shares of

Rite Aid

(RAD) - Get Report

fell 18% Friday after

CVS

(CVS) - Get Report

, the nation's largest drugstore chain, said it would not buy PCS Health Systems from its ailing rival.

The stock's decline followed a surge on Thursday after Rite Aid was reported to be close to selling the pharmacy benefits management business to CVS for $800 million to $1 billion. CVS is based in Woonsocket, R.I.

Rite Aid's stock dropped 1 5/8, to close at 7 3/8 Friday.

"It ran up on the basis that they might have a deal," said Philip Muldoon, an analyst at McDonald Investments, who rates Rite Aid a weak hold. "Whoever buys this thing, it eases the leverage on the balance sheet." McDonald Investments has not done any underwriting for the company.

Rite Aid, the second-largest drugstore chain, operates the PCS segment, which administers prescription benefits for more than 50 million customers.

There are still bidders left for the pharmacy benefits business, according to Karen Rugen, a Rite Aid spokeswoman. "We've had multiple bidders." But she declined to say who the suitors were.

"We need to sell it because we need to pay debt," Rugen said. "We're working on it diligently."

Rite Aid's stock has fallen more than 80% in the past year because of accounting problems. The Camp Hill, Pa.-based company was forced to restate its earnings for the last three years. The Securities and Exchange Commission is now investigating the company.

Rite Aid announced in November that it would sell several hundred West Coast drugstores and the PCS Health Systems to raise cash and pay off debt.