Any competitive 5-HT2A antagonist will block psychedelic effects from classical psychedelic drugs, and D2 antagonists will block the potential for stimulant-esque psychosis that drugs like LSD can trigger through dopamine agonism.<p>There are probably hundreds of drugs that fall into these classes, and many of them have significant clinical data to derive their safety profiles from.<p>If someone comes into a hospital with a bad reaction to psychedelic drugs, it's not uncommon for them to be given something like risperidone, both a 5-HT2A and D2 antagonist, and an anxiolytic to calm them down.