Mylan NV, a generic drug maker, sold $1 billion in bonds Friday to boost shareholders.

The company sold the notes, its first since 2013, in two equal parts and will use proceeds to fund share buybacks and repay debt, according to data compiled by Bloomberg. The longest-dated portion of the sale was $500 million of 3.75 percent five-year notes that yield 2.05 percentage points more than similar maturity Treasuries, Bloomberg data show.

While the price represented a "modest concession", some credit investors are concerned that the company risks being cut to junk if it embarks on an "overly aggressive acquisition," according to Eric Axon, an analyst at CreditSights Inc.

The notes were given a BBB- grade, which is one level above junk, by Fitch Ratings.

"You’re starting at a place where you’re at the lowest rung of high-grade so there’s not a lot of room to fail," Bloomberg Intelligence analyst Joel Levington said.

The drug-maker is likely to pursue debt-funded strategic buyouts after it was rebuffed in its $26 billion bid to buy Perrigo Co. earlier this year, which would cause the company’s credit measures to deteriorate, Standard & Poor’s said in a note on Nov. 13. S&P rates Mylan BBB-.

The bond sale comes a day after Mylan received a subpoena from the U.S. Department of Justice seeking information about its pricing practices.

Mylan initially marketed the 5-year notes at spreads that were much wider than the option adjusted spread Thursday on the company’s existing debt of similar maturity. The price tightened 0.20 percentage point by the time the offering sold.

Despite credit risk, buyers of Friday’s offering are probably lured to the debt because of the concession, according to Jerome Conner of Federated Investors Inc.

”Some people just buy based on valuation," he said.

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