The US Food and Drug Administration has approved Amitiza, a new drug for chronic constipation developed by Sucampo Pharmaceuticals.

Amitiza (lubiprostone) is the first in a new class of treatments for chronic constipation known as chloride channel activators, and works by increasing intestinal fluid secretion which, in turn, helps ease the passage of stool.

It will be marketed in the USA by Japanese drugmaker Takeda Pharmaceutical Industries, under the terms of a November 2004 agreement between the two companies in which Sucampo stood to receive up to $210 million in upfront and milestone payments.

The product will be available as capsules for use by adults to treat constipation that is not caused by other diseases or by use of medications, said the FDA in a statement.

The agency said it based its decision to approve Amitiza on the results from two clinical trials which showed that patients treated with Amitiza had a higher frequency of bowel movements in the first week than those on placebo, with that improvement maintained out to four weeks. Three long-term studies also showed that Amitiza decreased constipation severity, abdominal bloating and discomfort over six to 12 months of use.

Constipation, one of the most commonly reported digestive problems, affects more than 33 million US adults, causing 2.5 million doctor visits annually, according to Sucampo.

The drug is also in clinical testing for constipation-predominant irritable bowel syndrome.