Irsogladine, a mucosal protective drug, was developed in Japan for the treatment of peptic ulcer disease and acute gastritis. Irsogladine increases intracellular cyclic adenosine 3',5'-monophosphate content via non-selective inhibition of phosphodiesterase isozymes and exhibits gastric cytoprotection partly mediated by endogenous nitric oxide. These effects may account for a variety of actions of irsogladine in the gastrointestinal tract, including facilitation of gap junctional intercellular communication, inhibition of the reduced gastric mucosal blood flow response, suppression of reactive oxygen generation and so on.