Fluoxetine hydrochloride is the first agent of the class of antidepressants known as selective serotonin-reuptake inhibitors (SSRIs). Fluoxetine is a racemic mixture of the R- and S- enantiomers and are of equivalent pharmacologic activity. Despite distinct structural differences between compounds in this class, SSRIs possess similar pharmacological activity. As with other antidepressant agents, several weeks of therapy may be required before a clinical effect is seen. SSRIs are potent inhibitors of neuronal serotonin reuptake. They have little to no effect on norepinephrine or dopamine reuptake and do not antagonize α- or β-adrenergic, dopamine D2 or histamine H1 receptors. During acute use, SSRIs block serotonin reuptake and increase serotonin stimulation of somatodendritic 5-HT1A and terminal autoreceptors. Fluoxetine is marketed under the trade names Prozac and Sarafem among others. It is also marketed for the treatment of premenstrual dysphoric disorder (Sarafem®, fluoxetine hydrochloride). PROZAC is a selective serotonin reuptake inhibitor indicated for: • Acute and maintenance treatment of Major Depressive Disorder (MDD) in adult and pediatric patients aged 8 to 18 years • Acute and maintenance treatment of Obsessive Compulsive Disorder (OCD) in adult and pediatric patients aged 7 to 17 years • Acute and maintenance treatment of Bulimia Nervosa in adult patients • Acute treatment of Panic Disorder, with or without agoraphobia, in adult patients. Studies at clinically relevant doses in man have demonstrated that fluoxetine blocks the uptake of serotonin into human platelets. Studies in animals also suggest that fluoxetine is a much more potent uptake inhibitor of serotonin than of norepinephrine. Antagonism of muscarinic, histaminergic, and α1-adrenergic receptors has been hypothesized to be associated with various anticholinergic, sedative, and cardiovascular effects of classical tricyclic antidepressant (TCA) drugs. Fluoxetine binds to these and other membrane receptors from brain tissue much less potently in vitro than do the tricyclic drugs.

S-fluoxetine is an enantiomer of fluoxetine, a potent and selective inhibitor of the neuronal serotonin-uptake carrier and a clinically effective antidepressant. R-fluoxetine and S-fluoxetine enantiomers are nearly equipotent at blocking serotonin reuptake. In all biochemical and pharmacological studies, the eudismic ratio for the fluoxetine enantiomers is also near unity. A study examining the relative contributions of CYP enzymes to the metabolism of S-fluoxetine, and R-fluoxetine found dramatic differences. These data led to discovery programs between Lilly and Sepracor for the individual enantiomers. S-fluoxetine was studied in a phase 2 clinical trial for the prophylaxis of migraine, however, development was discontinued.

LY94939 was discovered as a result of efforts to develop agents that inhibit the uptake of 5-HT from the synaptic cleft. A selected analogue of LY94939, the compound LY82816 (3-p-trifluoromethyl-phenoxyN-methyl-3-phenylpropylamine oxalate or (fluoxetine oxalate), which was a secondary amine (later named as fluoxetine oxalate), and its primary amine or N-demethylated compound (later named as norfluoxetine), were the most potent inhibitors of [3 H]-5-HT uptake in nerve endings, with Ki values of 0.07 uM. The first salt form of fluoxetine tested in serotonin reuptake assays in the early 1970s was the oxalate salt (LY82816); however, the marketed version is the hydrochloride salt (fluoxetine hydrochloride (LY110140), or Prozac.

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.

Fluoxetine hydrochloride is the first agent of the class of antidepressants known as selective serotonin-reuptake inhibitors (SSRIs). Fluoxetine is a racemic mixture of the R- and S- enantiomers and are of equivalent pharmacologic activity. Despite distinct structural differences between compounds in this class, SSRIs possess similar pharmacological activity. As with other antidepressant agents, several weeks of therapy may be required before a clinical effect is seen. SSRIs are potent inhibitors of neuronal serotonin reuptake. They have little to no effect on norepinephrine or dopamine reuptake and do not antagonize α- or β-adrenergic, dopamine D2 or histamine H1 receptors. During acute use, SSRIs block serotonin reuptake and increase serotonin stimulation of somatodendritic 5-HT1A and terminal autoreceptors. Fluoxetine is marketed under the trade names Prozac and Sarafem among others. It is also marketed for the treatment of premenstrual dysphoric disorder (Sarafem®, fluoxetine hydrochloride). PROZAC is a selective serotonin reuptake inhibitor indicated for: • Acute and maintenance treatment of Major Depressive Disorder (MDD) in adult and pediatric patients aged 8 to 18 years • Acute and maintenance treatment of Obsessive Compulsive Disorder (OCD) in adult and pediatric patients aged 7 to 17 years • Acute and maintenance treatment of Bulimia Nervosa in adult patients • Acute treatment of Panic Disorder, with or without agoraphobia, in adult patients. Studies at clinically relevant doses in man have demonstrated that fluoxetine blocks the uptake of serotonin into human platelets. Studies in animals also suggest that fluoxetine is a much more potent uptake inhibitor of serotonin than of norepinephrine. Antagonism of muscarinic, histaminergic, and α1-adrenergic receptors has been hypothesized to be associated with various anticholinergic, sedative, and cardiovascular effects of classical tricyclic antidepressant (TCA) drugs. Fluoxetine binds to these and other membrane receptors from brain tissue much less potently in vitro than do the tricyclic drugs.

S-fluoxetine is an enantiomer of fluoxetine, a potent and selective inhibitor of the neuronal serotonin-uptake carrier and a clinically effective antidepressant. R-fluoxetine and S-fluoxetine enantiomers are nearly equipotent at blocking serotonin reuptake. In all biochemical and pharmacological studies, the eudismic ratio for the fluoxetine enantiomers is also near unity. A study examining the relative contributions of CYP enzymes to the metabolism of S-fluoxetine, and R-fluoxetine found dramatic differences. These data led to discovery programs between Lilly and Sepracor for the individual enantiomers. S-fluoxetine was studied in a phase 2 clinical trial for the prophylaxis of migraine, however, development was discontinued.

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.