The selective serotonin reuptake inhibitor fluoxetine consists of equal amounts of R and S stereoisomers (antidepressant Prozac (racemic fluoxetine). Binding to the transporter confirmed selectivity of R- and S-fluoxetine for the 5-HT transporter versus the dopamine (DA) and norepinephrine (NE) human transporters. In addition, receptor binding studies demonstrated significant affinity of R-fluoxetine, but not S-fluoxetine, for human 5-HT(2A) and 5-HT(2C) receptor subtypes. R-fluoxetine acts as an antagonist at 5-HT(2A) and 5-HT(2C) receptors. The attempt to develop a single-enantiomer formulation of fluoxetine for the treatment of depression was unsuccessful. Eli Lilly has terminated its licensing and development agreement with Marlborough, Mass.-based Sepracor for (R)-fluoxetine, the single-isomer version of Lilly's antidepressant Prozac.R-enantiomer of fluoxetine, at its highest administered dose, led to statistically significant prolongation of cardiac repolarization in phase II studies; the studies were subsequently stopped.

N,N-Diallyl-5-methoxytryptamine (N-Allyl-N-[2-(5-methoxy-1H-indol-3-yl)ethyl] prop-2-en-1- amine, 5-MeO-DALT) is a psychedelic tryptamine first synthesized by Alexander Shulgin. N,N-Diallyl-5-methoxytryptamine is used as a hallucinogenic drug has been reported only occasionally in online user fora. It is controlled in only a few countries worldwide. There is little scientifically-based literature on the pharmacological, physiological, psychopharmacological, toxicological and epidemiological characteristics of 5-MeO-DALT. Most of the information published on the effects of 5-MeO-DALT is derived from first-hand personal accounts presented in discussion fora. User reports suggest that its effects are felt within 15 min of being taken orally, and its full effects within 30 min. User reports on 5-MeO-DALT state rapid, strong entheogenic effect, euphoric, sensual, energised bodies, visual hallucinations (similar to those experienced with MDMA), loss of control of limbs making walking difficult, and ‘out of body’ type experience Acute mental effects reported include: increased alertness and awareness, increased arousal, and agitation.

AL-34662 is a potent, selective, and efficacious ocular hypotensive serotonin-2 receptor agonist. AL-34662 exhibited a high affinity for the rat and human 5-HT2 receptor (IC50=0.8-1.5 nM) and for cloned human 5-HT2A-C receptors (IC50=3-14.5 nM). AL-34662 is a high-affinity 5-HT2 receptor agonist that potently mobilizes [Ca2+]i in h-CM and h-TM cells, and which efficaciously lowers IOP in conscious ocular hypertensive cynomolgus monkey eyes through a local effect with minimal side-effects.

Lysergol {LYZ; (7-methyl- 4,6,6a,7,8,9-hexahydro-indolo[4,3-fg]quinolin-9-yl)-methanol} has shown potential to enhance BA of berberine (poorly water soluble herbal anticancer agent). It is obtained from the seeds of Ipomoea muricata, I. turbinate and Calonyction muricata belonging to the family Convolvulaceae. Seeds are commonly known as ‘Kaladana’ in trade and are being used as a purgative in India and Pakistan. LYZ is an indole alkaloid present in the microfungi of Claviceps purpurea as well. It is one of the minor constituents of the ancient Mexican hallucinogenic drug Ololiuqui, which is obtained from Rivea corymbosa seeds. LYZ has been used by the 17th century midwives to induce labour and stop postpartum bleeding because of its ability to induce uterine contractions. It may also cause ergot poisoning, diarrhea, hallucinations, delirium, seizures, burning sensations, and gangrene in the limbs. However, it is not being used presently in the clinic.

Lorcaserin, currently marketed under the trade name Belviq and previously Lorqess during development, is a weight-loss drug developed by Arena Pharmaceuticals. Lorcaserin is a selective 5-HT2C receptor agonist, and in vitro testing of the drug showed reasonable selectivity for 5-HT2C over other related targets. 5-HT2C receptors are located almost exclusively in the brain, and can be found in the choroid plexus, cortex, hippocampus, cerebellum, amygdala, thalamus, and hypothalamus. The activation of 5-HT2C receptors in the hypothalamus is supposed to activate proopiomelanocortin (POMC) production and consequently promote weight loss through satiety. This hypothesis is supported by clinical trials and other studies. While it is generally thought that 5-HT2C receptors help to regulate appetite as well as mood, and endocrine secretion, the exact mechanism of appetite regulation is not yet known. Lorcaserin has shown 100x selectivity for 5-HT2C versus the closely related 5-HT2B receptor, and 17x selectivity over the 5-HT2A receptor

Methysergide is an oral, synthetic ergot alkaloid, structurally related to the oxytocic agent methylergonovine and to the potent hallucinogen LSD. Methysergide is used prophylactically to reduce the frequency and intensity of severe vascular headaches. Although methysergide is an ergot alkaloid, it is a weak vasoconstrictor and oxytocic. Methysergide is a more potent antagonist of peripheral serotonin receptors than other ergot alkaloids. Methysergide is not just a 5HT2 antagonist, it is also a 5HT1 agonist. Although methysergide and sumatriptan both stimulate serotonin receptors centrally, methysergide is intended for prophylaxis while sumatriptan is indicated for treatment of an acute attack. Methysergide was approved by the FDA in 1962. Methysergide was formerly used for prophylaxis of cluster headaches/migraine headaches, but is no longer recommended due to retroperitoneal/retropulmonary fibrosis.

Sertindole (brand names: "Serdolect" and "Serlect") is an antipsychotic medication. Sertindole was developed by the Danish pharmaceutical company Lundbeck and marketed under license by Abbott Labs. Like other atypical antipsychotics, it has activity at dopamine and serotonin receptors in the brain. It is used in the treatment of schizophrenia. Sertindole is not approved for use in the United States and was discontinued in Australia in January 2014. In Europe, sertindole was approved and marketed in 19 countries from 1996, but its marketing authorization was suspended by the European Medicines Agency in 1998 and the drug was withdrawn from the market. In 2002, based on new data, the EMA's CHMP suggested that Sertindole could be reintroduced for restricted use in clinical trials, with strong safeguards including extensive contraindications and warnings for patients at risk of cardiac dysrhythmias, a recommended reduction in maximum dose from 24 mg to 20 mg in all but exceptional cases, and extensive ECG monitoring requirement before and during treatment.

Setiptiline Maleate is a tetracyclic antidepressant that has been used in the treatment of depression. It has antihistamine and hypnotic–sedative effects, but almost no anticholinergic effects. It is a weak inhibitor of norepinephrine reuptake in vitro and strongly stimulates the release of central norepinephrine by blocking presynaptic α2-adrenoceptors similar to mianserin. It also acts as a 5-HT2A, 5-HT2C, and 5-HT3 receptor antagonist. Unlike most conventional antidepressants, it has no efficacy as a serotonin reuptake inhibitor. It can induce drowsiness and thirst, but it displays low toxicity. Setiptiline Maleate was launched in 1989 for the treatment of depression in Japan.