Quintiles Transnational Corp. is paying as much 50 percent more for a $300 million loan than on a similar borrowing in June, burdening the company with increased interest costs to fund its second dividend in a year to Bain Capital LLC and TPG Capital.

The biggest provider of testing and drug-trial services to pharmaceutical and biotech firms will pay a fixed 7.5 percent on the five-year credit, according to data compiled by Bloomberg. It pays a minimum 5 percent on a $2 billion floating-rate, seven-year term loan it obtained last year, also used to finance a dividend to its private-equity owners, the data show.

Bain, TPG and other owners are taking advantage of Quintiles's cash flow to collect roughly $1 billion of distributions in little more than two years, according to Bloomberg data and reports from Moody's Investors Service. The new loan, due in 2017, represents $23 million of annual interest costs and will finance most of a $335 million payout, limiting the junk-rated company's ability to obtain upgrades.