The pharmacy benefit management industry Friday criticized a health-care bill provision to require more disclosure from PBMs, saying the measure would raise rather than lower prescription drug costs.

The Senate Finance Committee adopted an amendment by Sen. Maria Cantwell, D-Wash., to require disclosure of certain information from PBMs participating in health insurance exchanges or the Medicare Part D drug program.

PBMs handle prescription drug benefits for employer and health-plan clients and the individuals covered by those plans, negotiating prices and discounts with drug makers and pharmacies. Cantwell's amendment would require PBMs to disclose the difference between what plans pay them for drugs and the amount the PBMs actually pay to purchase the drugs from retail and mail-order pharmacies.

The Pharmaceutical Care Management Association, which represents PBMs such as Medco Health Solutions Inc. (MHS), Express Scripts Inc. (ESRX) and CVS Caremark Corp. (CVS), said the measure would give drug makers more pricing power while not helping consumers.

PBMs "believe strongly in the principal of transparency and empowering payers to make informed health-care purchasing decisions resulting in lower prescription drug costs and higher quality. Regrettably, today's amendment moves the health-care system in the opposite direction," PCMA President Mark Merritt said in a statement. "The Cantwell amendment would force PBMs to disclose information that would give manufacturers and drug stores more leverage in drug-price negotiations."

The amendment would require PBMs to share information with the Secretary of Health and Human Services and with health plans they contract with through the Medicare prescription-drug-benefit program or the health insurance exchanges proposed by the underlying health-overhaul bill. The information is to be considered confidential.

Among other data, PBMs would have to disclose the aggregate amount and types of rebates and price concessions they negotiate on behalf of a plan and the aggregate amount passed along to the plan sponsor.

"I think there's a slippery-slope issue and also the issue of confidentiality has always been in question," Merritt told Dow Jones Newswires. "This kind of transparency has never reduced prices," according to serious economists who have looked at it, he added.

The House Energy and Commerce Committee previously approved a similar provision in its health-care overhaul bill.

"PBM business practices and pricing have always been somewhat opaque and increased disclosure could negatively impact margins," said Wells Fargo analyst Matt Perry. "Pricing information could help pharma companies and retail pharmacy chains get better pricing out of PBMs, which could decrease the value that PBMs are able to provide to their employer customers, as well as hurt PBM margins." He noted that the measure is a long way from being written into law.

Earlier this week, the National Community Pharmacists Association voiced support for the measure, saying it would drive down health-care costs by lifting "a shroud of secrecy" that has allowed PBMs "to pocket large portions of both the transactions they process as well as the rebates paid by manufacturers."

PBMs could benefit from other aspects of a revision of the nation's health laws. Provisions to expand health coverage to millions more Americans and to promote the use of generic drugs are considered positive for the industry.

Medco recently traded down less than 1% to $54.88 and Express Scripts was off 1.3% at $76.99. CVS Caremark, which also operates the national CVS drug-store chain, was up 3 cents at $35.23.

-By Dinah Wisenberg Brin, Dow Jones Newswires; 215-656-8285; dinah.brin@dowjones.com

(Patrick Yoest contributed to this article.)