Endo Pharma intends to finance the deal with $500m from its balance sheet, while securing a $300m credit line and tapping an additional $400m financing.
Endo Pharma, a maker of branded and generic drugs to mainly treat and manage pain, overactive bladder, and prostate and bladder cancer, expects the deal to add $400m in revenue, Reuters reported.
The combined entity will have revenue of about $2bn with more than 3,000 employees.
Endo and Qualitest have 46 generic-drug applications under review by the US Food and Drug Administration, including treatments for cancer, hypertension and pain, Chadds Ford, Pennsylvania-based Endo said.
Reportedly, Apax purchased Qualitest and Vintage Pharmaceuticals for $900m in 2007.
The sale comes at a time when several private-equity firms have been off-loading assets through divestitures and initial public offerings as they monetise holdings.