fizer has followed in the footsteps of Roche and has placed an unspecified number of bonds to raise around $13.5 billion in a debt offering that will help finance its $68 billion acquisition of Wyeth.

The New York-based behemoth has put in motion a five-part issue which offered bonds that mature in two, three, six, ten and thirty years, with yields ranging from 3.25% to 7.25%. Financial observers are saying that Pfizer could have offered twice as many bonds, such has been the demand.

The deal to buy Wyeth involved Pfizer getting a bridge loan of $22.5 billion off five major investment banks. These in turn have syndicated portions of the loan to 29 other banks, with none of them financing more than $1.5 billion of the total.

However that loan is set to expire at the end of the year so Pfizer is replacing much of the short-term debt earlier than it strictly needs to with the bonds offer. The company is expected to reveal more about the offering in the next couple of days.

Pfizer’s move follows a similar strategy adopted at the end of February by Roche which raised more than $30 billion in bond issues on both sides of the Atlantic. The Swiss firm is using the funds to help finance its $46.8 billion bid for the 44.2% stake in Genentech it does not already own.