Further consolidation in the pharmacy benefits management business is only a matter of time, CVS Caremark Corp. (CVS) Chief Financial Officer David Rickard (CVS) said Friday.

Speaking at Thomas Weisel Partners Healthcare Conference in Boston, Rickard didn't indicate whether CVS would be interested in making acquisitions of other pharmacy benefit management companies, or PBMs. However, in an interview with Dow Jones Newswires last month, he didn't rule out the possibility of at least considering them.

Market share should continue to gravitate toward major PBM players, which because of their size have better buying power when purchasing drugs, Rickard said. Besides Caremark, the other two top PBMs are Express Scripts Inc. (ESRX) and Medco Health Solutions Inc. (MHS).

CVS Caremark is a hybrid drugstore retailer and pharmacy benefits manager, formed when the drugstore giant acquired Caremark for $27 billion in 2007.

"Certainly, the efficiency of the top three is greater than the efficiency of those below," Rickard said Friday.

As major PBMs keep gaining share, "what won't happen is some of those in the non-top three will become, you know, competitively unfit, and so there will be a further consolidation within the industry," he said.

Consolidation in the PBM industry has been a focus for investors, after Express Scripts announced its purchase of health insurer WellPoint Inc.'s (WLP) in-house PBM in April.

Cigna Corp. (CI) has indicated an interest in placing its PBM for sale, and The Wall Street Journal has reported that Aetna Inc. (AET) put its drug-benefits business on the block.

Some in the industry have said CVS could be a potential suitor in the Aetna PBM deal, but CVS has said it does not comment on rumors related to specific acquisitions or mergers.

In recent trading, shares of CVS were down slightly, off 17 cents, or 0.5% to $36.50.

-By Kelly Nolan; Dow Jones Newswires; 212-416-2167; kelly.nolan@dowjones.com