A drug deal that is mainly about the drugs.

That was many analysts’ assessment Monday of Merck’s agreement to pay $41.1 billion in cash and stock for Schering-Plough. The merger would join pharmaceutical companies that had combined sales of $46.9 billion last year.

Mega-mergers of this sort have been widely expected ever since Pfizer began the consolidation race in January by agreeing to pay $68 billion for Wyeth. And others are likely to follow, as many of the same factors — like expiring patents and soaring development costs — propel drug makers into one another’s arms.

But if Pfizer-Wyeth was driven in part by desperation, analysts said, for Merck the Schering deal may actually be a good opportunity to restock its medicine chest. Merck’s former blockbuster bone drug Fosamax has gone generic, and in a few years the same thing will happen to its best-selling allergy and asthma drug Singulair. The merger gives it access to successful brand-name Schering products with much longer patents, like the prescription allergy spray Nasonex. And Merck could capitalize on Schering’s investments in promising biotechnology drugs.

“It’s better than the other deal,” Robert Hazlett, an analyst with BMO Capital Markets, said of the Merck-Schering merger. “I’m not enamored of Pfizer-Wyeth.”