The purchase would create the nation's biggest drug wholesaler, with about 31 percent of the annual $64 billion market.
In a separate ruling, the judge granted a motion to dismiss six drug wholesalers from the suit.
Having a highly fragmented retail distribution system, it was normal for companies to operate through about one thousand drug wholesalers.
The agency did a detailed comparison of prices that American companies charged drug wholesalers for 121 drugs.
Mr. Treppel said another question was how the other big drug wholesalers would react.
It is logical, the analysts believe, for drug wholesalers to do the same.
The margins for drug wholesalers are very low, and they should be allowed to do what's necessary to become more efficient.
Analysts said the number of drug wholesalers dwindled to 55 last year from 139 companies in 1980.
A Federal judge has blocked two mergers involving four of the nation's biggest drug wholesalers.
Cardinal Health, the big drug wholesaler, declined $5.66, or 10 percent, to $52.68.
