Xylamidine is a drug which acts as an antagonist of the serotonin 5-HT2A and 5-HT2C receptors, and to a lesser extent of the serotonin 5-HT1A receptor. The drug does not cross the blood–brain barrier and hence is peripherally selective, which makes it useful for blocking peripheral serotonergic responses like cardiovascular and gastrointestinal effects, without producing the central effects of 5-HT2A receptor blockade such as sedation, or interfering with the central actions of 5-HT2A receptor agonists.