Merck & Co. and Walgreen Co. led borrowers selling $17.9 billion of corporate bonds in the U.S. Monday.

Merck, the maker of Claritin, raised $2.5 billion of debt in three parts in its first sale since 2010 and Deerfield, Illinois-based Walgreen issued $4 billion of bonds linked to its acquisition of a stake in Alliance Boots Holdings Ltd., according to data compiled by Bloomberg. Sales compare with $18.6 billion on Sept. 4, the busiest day for dollar-denominated sales in almost six months.

Issuers are selling bonds ahead of a meeting this week by the U.S. Federal Reserve, where policy makers may announce further quantitative easing. Companies are timing the market to obtain record-low interest rates as they capitalize on high demand ahead of potential volatility, according to Rob Crimmins, a money manager in New York at RS Investments, which oversees $30 billion.