Merck & Co., Inc. (NYSE:MRK), the Whitehouse Station, N.J.-based pharmaceutical giant that makes Claritin, is borrowing about $2.5 billion at a bargain-basement interest rate to service debt and contribute to its pension fund.

The move, which Merck said Wednesday will come by issuing three tranches of bonds, increases the company's total debt to $21.47 billion from $18.98 billion. After various expenses from the bond offering, the net proceeds are expected to be $2.48 billion.

The interest rates Merck will have to pay on the borrowed money range from 1.1 percent to 3.6 percent.

The move is the first such borrowing for Merck since December 2010, Bloomberg News said.