Levomilnacipran (1S, 2R/F2695) is an enantiomer of milnacipran, a serotonin/norepinephrine (5-HT/NE) reuptake inhibitor. Levomilnacipran is pharmacologically more active as compared with racemic mixture and dextromilnacipran (1R, 2S/F2696). The safety of the drug is also higher than the safety of a racemate, resulting in a beneficial impact on the therapeutic effect. Pierre Fabre and Forest Laboratories are developing levomilnacipran extended release (ER) [FETZIMA™], an enantiomer of milnacipran, for the treatment of major depressive disorder (MDD). In addition, Pierre Fabre (the originator of the compound) is developing the drug to improve recovery in patients with ischaemic stroke.

Dextromilnacipran (1R, 2S/F2696) is an enantiomer of milnacipran, a serotonin/norepinephrine (5-HT/NE) reuptake inhibitor. Dextromilnacipran is pharmacologically less active as compared with racemic mixture and levomilnacipran (1S, 2R/F2695).

Desvenlafaxine is a dual serotonin and norepinephrine reuptake inhibitor in vitro and in vivo that demonstrates good brain-to-plasma ratios. Desvenlafaxine has demonstrated antidepressant effects in preclinical studies. Pfizer is developing an oral, extended-release formulation of desvenlafaxine for the treatment of major depressive disorder. Desvenlafaxine has been registered and is available on the market for the treatment of major depressive disorder in adults.

Atomoxetine is indicated for the treatment of Attention-Deficit/Hyperactivity Disorder. The precise mechanism by which atomoxetine produces its therapeutic effects in Attention-Deficit/Hyperactivity Disorder (ADHD) is unknown, but is thought to be related to selective inhibition of the pre-synaptic norepinephrine transporter. Most common adverse reactions are: nausea, vomiting, fatigue, decreased appetite, abdominal pain, and somnolence, constipation, dry mouth, dizziness, erectile dysfunction, and urinary hesitation. Atomoxetine is a substrate for CYP2D6 and hence concurrent treatment with CYP2D6 inhibitors such as bupropion (Wellbutrin) or fluoxetine (Prozac) is not recommended, as this can lead to significant elevations of plasma atomoxetine levels.

Succinic acid is a dicarboxylic acid, which has multiple biological roles as a metabolic intermediate being converted into fumarate by the enzyme succinate dehydrogenase in complex 2 of the electron transport chain which is involved in making ATP, and as a signaling molecule reflecting the cellular metabolic state. Succinate is generated in mitochondria via the tricarboxylic acid cycle (TCA), an energy-yielding process shared by all organisms. Succinate can exit the mitochondrial matrix and function in the cytoplasm as well as the extracellular space, changing gene expression patterns, modulating epigenetic landscape or demonstrating hormone-like signaling. Dysregulation of succinate synthesis, and therefore ATP synthesis, happens in some genetic mitochondrial diseases, such as Leigh's disease, and Mela's disease and degradation can lead to pathological conditions, such as malignant transformation, inflammation and tissue injury. Succinic acid is a precursor to some polyesters and a component of some alkyd resins. Succinic acid also serves as the bases of certain biodegradable polymers, which are of interest in tissue engineering applications. As a food additive and dietary supplement, succinic acid is generally recognized as safe by the U.S. Food and Drug Administration. Succinic acid is used primarily as an acidity regulator in the food and beverage industry. It is also available as a flavoring agent, contributing a somewhat sour and astringent component to umami taste.[11] As an excipient in pharmaceutical products, it is also used to control acidity or as a counter ion. Drugs involving succinate include metoprolol succinate, sumatriptan succinate, Doxylamine succinate or solifenacin succinate.