High Quality Content by WIKIPEDIA articles! Xylamidine is a drug which acts as an antagonist at the 5HT2A receptor, and to a lesser extent at the 5HT1A receptor. It does not cross the blood brain barrier which makes it useful for blocking peripheral serotonergic responses like cardiovascular and gastrointestinal effects, without producing the central effects of 5HT2A blockade such as sedation, or interfering with the central actions of 5HT2A agonists.