DineEquity Inc., the owner of the IHOP and Applebee’s restaurant chains, has completed the refinancing of $472 million in debt, the company announced Tuesday. The Glendale restaurant operator said it would now pay an effective loan rate of 3.75 percent on its senior secured credit facility, including $75 million in revolving debt. Two years ago, the company had reduced the interest rate on the facility to 4.25 percent from 6 percent. DineEquity took on substantial debt in 2007 when it acquired the Applebee’s Grill & Bar chain for $2.1 billion. It has since been paying down that debt through a strategy that has involved franchising nearly all of its restaurant outlets. Shares were down 9 cents to $73.86 in after-hours trading on the Nasdaq.