The company said that total consideration for the product was $12m including an $11m upfront payment and a $1m future milestone payment.
ANI intends to launch Lithobid under its own label in July 2014.
The transaction is immediately accretive and is expected to generate about $4m in revenues and $3.9m in non-GAAP EBITDA annually.
ANI president and CEO Arthur Przybyl said the company is happy to add Lithobid to its portfolio of mature brand products.
"Prior to the acquisition, ANI contract manufactured Lithobid, which allows us to immediately launch ANI-labeled product," Przybyl said.
"This transaction represents our second mature brand acquisition and underscores our strategy of augmenting internal generic product development efforts with acquisitions and partnerships for late stage ANDA products and mature brands."
ANI develops, manufactures and markets branded and generic prescription pharmaceuticals and its targeted areas of product development currently include narcotics, oncolytics (anti-cancers), hormones and steroids, and complex formulations involving extended release and combination products.