Aliment Pharmacol Ther 2011; 34: 868–877

Background  There is a need for safe and effective treatment options for irritable bowel syndrome (IBS). AST‐120 (spherical carbon adsorbent) is a non‐absorbed, carbon‐based adsorbent with extensive adsorbing capability for histamine, serotonin and other substances implicated in IBS pathogenesis.

Aim  To evaluate the efficacy and safety of AST‐120 in non‐constipating forms of IBS.

Methods  This randomised, double‐blind, placebo‐controlled trial conducted in the US and Belgium enrolled 115 male and female patients fulfilling Rome III criteria for IBS; individuals with predominantly constipation symptoms were excluded. Subjects were randomised to AST‐120 2 g tds or placebo for an 8‐week double‐blind treatment period, followed by a 2‐week single‐blind placebo washout and 8‐week single‐blind active treatment. The primary efficacy endpoint was the proportion of subjects achieving at least a 50% reduction in the number of days with abdominal pain compared with baseline.

Results  At Week 4, 26.8% of subjects treated with AST‐120 responded on the primary endpoint vs. 10.2% in the placebo arm (P = 0.029); at Week 8 response rates were 32.1 and 25.4% respectively (NS). More AST‐120 treated subjects experienced improvement in bloating and stool consistency. These benefits abated when AST‐120 was replaced by placebo, and resumed once AST‐120 was restarted. The frequency of adverse events with AST‐120 were less than or equal to placebo.

Conclusions  AST‐120 is safe and well‐tolerated and reduces pain and bloating in non‐constipating IBS, although beneficial effects may be limited in duration. AST‐120 represents a locally acting, non‐absorbed, novel treatment for IBS and warrants further studies.