Eplivanserin (SR 46349) is an antagonist of serotonin 2A receptor. Eplivanserin was previously in development by Sanofi-aventis in an effort to educate the public regarding this new mechanism of action for sleep aids. Eplivanserin was reviewed by the FDA as a potential treatment for patients with chronic insomnia, but the FDA requested additional information regarding benefit-risk and development of the drug has been discontinued.

PNU-96391A (known as OSU6162) is a weak dopamine (DA) D(2) receptor antagonist with behavioral stabilizing properties. OSU6162 seem to act as stabilizers not only on dopaminergic, but also on serotonergic brain signaling (partial agonist on 5-HT2A receptor). OSU6162 in a phase II European clinical trial in treatment of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome. One of the isomer of OSU 6162, has promise for treating Parkinson's disease, Huntington's disease and schizophrenia, but both enantiomers of OSU 6162 had dual effects on behavior, stimulating locomotor activity in 'low activity' animals and inhibiting locomotor activity in 'high activity' animals.

CYR-101 (MIN-101) is a cyclic amide derivative that has high equipotent affinities for 5-HT2A and sigma-2 receptors (Ki of 7.53 nM and 8.19 nM for 5-HT2A and sigma-2, respectively). MIN-101 also shows binding affinity for a1-adrenergic receptors but low or no affinity for muscarinic, cholinergic, and histaminergic receptors. MIN-101 demonstrated statistically significant efficacy in reducing negative symptoms and good tolerability in stable schizophrenia patients. The drug is in phase II clinical trials for the treatment of Schizophrenia.

Pruvanserin (EMD 281014, LY-2422347) is a selective serotonin 5-HT2A receptor antagonist. Pruvanserin was originated by Merck KGaA. Eli Lilly had been developing pruvanserin, under a global licence from Merck KGaA, for the treatment of primary insomnia and major depressive disorder. Phase II trials were completed in the US, Hungary and Spain. However, development appears to have been discontinued.

m-Chlorophenylpiperazine (meta-chlorophenylpiperazine or mCPP) is a psychoactive substance, which is illegal in many countries but can be found on the black market. It induces endocrine, neurological and psychiatric effects. mCPP is a partial agonist at the 5-HT2C receptor but antagonized the 5-HT2B and 5-HT3 receptors. mCPP is also an active metabolite of the drug trazodone, which is used as an effective antidepressant drug with a broad therapeutic spectrum, including anxiolytic efficacy. It is known, that mCPP induces migraine attacks and that the decrease of food intake induced by the mCPP depends on its ability to act as a serotonin agonist is a brain.

Lysergide (LSD) is a semi-synthetic hallucinogen and is one of the most potent drugs known. Recreational use became popular between the 1960s to 1980s, but is now less common. LSD was first synthesized by Albert Hoffman while working for Sandoz Laboratories in Basel in 1938. Some years later, during a re-evaluation of the compound, he accidentally ingested a small amount and described the first ‘trip’. During the 1950s and 1960s, Sandoz evaluated the drug for therapeutic purposes and marketed it under the name Delysid®. It was used for research into the chemical origins of mental illness. Recreational use started in the 1960s and is associated with the ‘psychedelic period’. LSD possesses a complex pharmacological profile that includes direct activation of serotonin, dopamine and norepinephrine receptors. In addition, one of its chief sites of action is that of compound-specific (“allosteric”) alterations in secondary messengers associated with 5HT2A and 5HT2C receptor activation and changes in gene expression. The hallucinogenic effects of LSD are likely due to agonism at 5HT2A and 5HT2C receptors. LSD is also an agonist at the majority of known serotonin receptors, including 5HT1A, 5HT1B, 5HT1D, 5HT5A, 5HT6 and 5HT7 receptors. During the 1960s, LSD was investigated for a variety of psychiatric indications, including the following: as an aid in treatment of schizophrenia; as a means of creating a "model psychosis"; as a direct antidepressant; and as an adjunct to psychotherapy. LSD is listed in Schedule I of the United Nations 1971 Convention on Psychotropic Substances.

Lysergide (LSD) is a semi-synthetic hallucinogen and is one of the most potent drugs known. Recreational use became popular between the 1960s to 1980s, but is now less common. LSD was first synthesized by Albert Hoffman while working for Sandoz Laboratories in Basel in 1938. Some years later, during a re-evaluation of the compound, he accidentally ingested a small amount and described the first ‘trip’. During the 1950s and 1960s, Sandoz evaluated the drug for therapeutic purposes and marketed it under the name Delysid®. It was used for research into the chemical origins of mental illness. Recreational use started in the 1960s and is associated with the ‘psychedelic period’. LSD possesses a complex pharmacological profile that includes direct activation of serotonin, dopamine and norepinephrine receptors. In addition, one of its chief sites of action is that of compound-specific (“allosteric”) alterations in secondary messengers associated with 5HT2A and 5HT2C receptor activation and changes in gene expression. The hallucinogenic effects of LSD are likely due to agonism at 5HT2A and 5HT2C receptors. LSD is also an agonist at the majority of known serotonin receptors, including 5HT1A, 5HT1B, 5HT1D, 5HT5A, 5HT6 and 5HT7 receptors. During the 1960s, LSD was investigated for a variety of psychiatric indications, including the following: as an aid in treatment of schizophrenia; as a means of creating a "model psychosis"; as a direct antidepressant; and as an adjunct to psychotherapy. LSD is listed in Schedule I of the United Nations 1971 Convention on Psychotropic Substances.