Nearly half of Boston Scientific Corp.‘s massive $6 billion-plus debt will come due in April 2011.

The company’s total tab is $6.25 billion, with an average interest rate of 5.84 percent. At the end of 2008, the company owed more than $6.78 billion, but has paid down about $500 million since January, at least some of it on the backs of Peter Nicholas and John Abele.

The BSC co-founders sold an enormous amount of personal stock in the company over the past six months.

What’s potentially more alarming for the Natick medical devices colossus and its stockholders is that April 2011 due date on $3.75 billion in loans and senior notes.

Specifically, the company owes $850 million in senior notes, $900 million on a 4 percent unsecured loan from Abbott and a $2 billion payment on a term loan.

The company also owes $325 million on that term loan, due next April.

Boston Scientific recently reported a $13 million first-quarter net loss, despite posting more than $2 billion in sales.

But it’s that looming deadline that’s likely on the minds of the denizens in the Natick executive suite.

During a conference call with investors April 21, CFO Sam Leno commented on the deadline:

“We have a long, 24-month runway to determine the best way to repay this debt.”

BSC’s already spent $2.7 billion in the last two years paying off debt, Leno added. What the company does in the next 23 months may determine its future.

So don’t expect BoSci to get in on the bargains available on the M&A market. For now, it’s probably all about debt management.

Or at least it should be.