File photo. Ali Banijamali, principal investigator, is preparing to purify compounds for analysis working with compounds at Ironwood Pharmaceuticals labs. ( David L Ryan / Globe Staff.)
File photo. Ali Banijamali, principal investigator, is preparing to purify compounds for analysis working with compounds at Ironwood Pharmaceuticals labs. ( David L Ryan / Globe Staff.)

Cambridge-based Ironwood Pharmaceuticals Inc. reported a “strong” launch for Linzess, its new drug designed to treat irritable bowel syndrome, or IBS, with constipation.

Ironwood is marketing the drug with Forest Laboratories Inc. In a Tuesday press release, Ironwood said that Forest reported net product sales of $28.8 million for Linzess during its second quarter.

Citing IMS Health data, Ironwood said that more than 125,000 Linzess prescriptions were filled in the second quarter of 2013 and more than 200,000 Linzess prescriptions have been filled since Linzesss launched on Dec. 17.

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Because IBS is estimated to afflict 30 million to 40 million Americans, some stock analysts have predicted that the Ironwood drug could attain blockbuster status — ringing up sales of more than $1 billion a year worldwide — within a decade.

In a statement included with Tuesday’s release, Ironwood chief executive Peter Hecht said: “The past six months have been a transformative period at Ironwood, thanks to the dedication and hard work of our team. The Linzess launch is strong and tracking well across all leading indicators, and we and Forest are working closely together to drive all aspects of the launch. At the same time, together with Forest we are making progress in our efforts to maximize the commercial and clinical success of Linzess by exploring ways to strengthen the existing label and seeking regulatory approval for Linzess in additional populations and indications.”