A pharmaceutical composition for preventing and treating pancreatitis comprising asan active ingredient, a 5-HT2A receptor antagonist, characterized in that thebinding activity (pKi) of the 5-HT2A receptor antagonist to 5-HT2A receptor ishigher by a value of not less than 1.0 than the binding activity to 5-HT2B and 5-HT2Creceptors is disclosed. The binding activity (pKi) of the 5-HT2A receptor antagonistto 5-HT2A receptor is preferably 7.0 or higher and more preferably 8.0 or higher.The invention also provides a method of identifying a candidate substance ofthe agent for preventing/treating pancreatitis comprising measuring whetheror not a test substance has a 5-HT2A receptor antagonism.
