Merck & Co.'s (MRK) planned purchase of Schering-Plough Corp. (SGP) may not in itself spell trouble for pharmaceutical industry middlemen, but the deal - along with others in the industry - could add pressure for distributors as yet another key supplier gets bigger.

Drug distributors didn't appear fazed by the deal between Merck and Schering-Plough, valued at $41.1 billion based on Merck's Friday closing price, noting their good relationships with both drug manufacturers. However, because of the recent industry consolidation, including Pfizer Inc.'s (PFE) planned acquisition of Wyeth (WYE), drug makers are seen gaining more leverage over wholesalers.

"In general, the consolidation of manufacturers is bad for wholesalers because it's giving the drug makers much more leverage in their fee-for-service negotiations," said Adam Fein, president of Pembroke Consulting in Philadelphia, a pharmaceutical supply chain consultancy. Fein, though, didn't see significant differences between Merck and Schering-Plough in their current relationships with distributors.

"This deal is not a game changer for the wholesalers, but it's one more pressure point on their business," Fein said.

To some, brand-name prescription drug makers already had more leverage because of monopolies on their patent-protected products - a fact that consolidation doesn't change.

AmerisourceBergen Corp. (ABC), Cardinal Health Inc. (CAH) and McKesson Corp. (MCK) act as wholesalers of prescription drugs, and are paid, partly, by manufacturers to package and otherwise add value to the products, which they distribute to pharmacies and hospitals.

In recent years, the drug wholesaler industry shifted from a largely buy-and-hold compensation model based on drug-price inflation to a fee-for-service model in which manufacturers pay them to package and otherwise add value to the products.

"We have a great relationship with both companies and see little or no impact to AmerisourceBergen," company spokesman Michael Kilpatric said.

Cardinal Health spokesman Troy Kirkpatrick said, "It is too premature to determine any potential impact to Cardinal Health, but we have great relationships with both of these partners and look forward to working with them both individually until the merger occurs and then beyond post-merger."

A McKesson spokesman said the company doesn't comment on its suppliers.

The recently announced Pfizer-Wyeth deal, meanwhile, might have more of a direct effect on the wholesalers because Pfizer is just now adopting fee-for-service contracts with the distributors, and its terms could differ from those of Wyeth, Pembroke Consulting's Fein said.

The larger a manufacturer, the more sales volume it controls, and therefore the more power it wields in negotiations, Fein said.

And while the Merck deal probably won't create a huge movement toward manufacturers having direct relationships with buyers such as drugstore chains, major mail-order pharmacies and Wal-Mart Stores Inc. (WMT), Fein said it is one more step in that direction.

The chain drugstores, Wal-Mart and pharmacy benefit managers' mail-order pharmacies account for more than half of all prescription volume in the U.S., he said.

Fein didn't expect much of an effect from the deal on pharmacy benefit managers as their contracts with manufacturers tend to be based on individual products.

A spokeswoman for pharmacy benefits manager Express Scripts Inc. (ESRX) said the company doesn't comment on such announcements. Medco Health Solutions Inc. (MHS), another pharmacy benefits manager, had no immediate comment. PBMs arrange prescription-drug benefits for employers and their employees, and also operate mail-order pharmacies.

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