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.

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.

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.

Promazine (Sparine) is a phenothiazine neuroleptic used for short-term management of moderate to severe psychomotor agitation and treatment of agitation and restlessness in the elderly. Promazine is an antagonist at types 1, 2, and 4 dopamine receptors, 5-HT receptor types 2A and 2C, muscarinic receptors 1 through 5, alpha(1)-receptors, and histamine H1-receptors. Promazine's antipsychotic effect is due to antagonism at dopamine and serotonin type 2 receptors, with greater activity at serotonin 5-HT2 receptors than at dopamine type-2 receptors. This may explain the lack of extrapyramidal effects. Promazine does not appear to block dopamine within the tuberoinfundibular tract, explaining the lower incidence of hyperprolactinemia than with typical antipsychotic agents or risperidone. Antagonism at muscarinic receptors, H1-receptors, and alpha(1)-receptors also occurs with promazine. Promazine is not approved for human use in the United States. It is available in the US for veterinary use under the names Promazine and Tranquazine.

Promazine (Sparine) is a phenothiazine neuroleptic used for short-term management of moderate to severe psychomotor agitation and treatment of agitation and restlessness in the elderly. Promazine is an antagonist at types 1, 2, and 4 dopamine receptors, 5-HT receptor types 2A and 2C, muscarinic receptors 1 through 5, alpha(1)-receptors, and histamine H1-receptors. Promazine's antipsychotic effect is due to antagonism at dopamine and serotonin type 2 receptors, with greater activity at serotonin 5-HT2 receptors than at dopamine type-2 receptors. This may explain the lack of extrapyramidal effects. Promazine does not appear to block dopamine within the tuberoinfundibular tract, explaining the lower incidence of hyperprolactinemia than with typical antipsychotic agents or risperidone. Antagonism at muscarinic receptors, H1-receptors, and alpha(1)-receptors also occurs with promazine. Promazine is not approved for human use in the United States. It is available in the US for veterinary use under the names Promazine and Tranquazine.