Tryptophan is alpha-aminoacid that is used in the biosynthesis of proteins. It is essential aminoacid in humans, meaning the body cannot synthesize and it must be obtained from the diet. Tryptophan is a precursor of serotonin, and as such is sold over the counter in many countries as a dietary supplement for use as an antidepressant, anxiolytic and sleep aid, however application of tryptophan in these indications is not approved by FDA.

Bifemelane is a psychotropic drug, was found to inhibit monoamine oxidase (MAO). It inhibited type A MAO (MAO-A) competitively and type B (MAO-B) noncompetitively and it was a more potent inhibitor of MAO-A than of MAO-B. Bifemelane is an antidepressant and cerebral activator that is used in Japan for the treatment of cerebral infarction patients with depressive symptoms, and in the treatment of senile dementia as well. It also appears to be useful in the treatment of glaucoma.

TIANEPTINE, a tricyclic antidepressant, is a drug used for the treatment of the major depressive disorder. It was discovered by The French Society of Medical Research in the 1980s. Unlike other tricyclic antidepressants, TIANEPTINE is a selective serotonin reuptake enhancer with minimal effects on norepinephrine and dopamine uptake. Also, it is a full agonist at the mu-opioid and delta-opioid receptors with no effect at the kappa-opioid receptors. Selective mu-opioid agonists typically induce euphoria, which may contribute to TIANEPTINE's antidepressant effect. It is marketed as Coaxil/Stablon in many European countries, but it is not available in the US.

Oxaflozane is non-tricyclic antidepressant with serotoninergic action. In animals, oxaflozane has anti-cataleptic and anti-aggressive action with weak potentiation of stereotypes provoked by amphetamine. Oxaflozane was developed by Solvay Pharma and marketed in France under tradename Conflictan. The drug was discontinued in 2004.

Agomelatine behaves both as a potent agonist at melatonin MT1 and MT2 receptors and as a neutral antagonist at 5-HT2C receptors. Accumulating evidence in a broad range of experimental procedures supports the notion that the psychotropic effects of agomelatine are due to the synergy between its melatonergic and 5-hydroxytryptaminergic effects. Agomelatine is indicated for the treatment of major depressive episodes.

Reboxetine is a selective noradrenergic reuptake inhibitor that acts by binding to the norepinephrine (NE) transporter and blocking reuptake of extracellular NE back into terminals. This compound has low affinity for other transporters and receptors. Reboxetine is used in acute treatment of depressive illness / major depression. Very common side effects are: difficulties to sleep (insomnia); dizziness; dry mouth; constipation; nausea (feeling sick); sweating. Based on studies conducted primarily outside the US, the FDA granted a preliminary letter of approval in 1999. However, more recent clinical studies conducted in the US and Canada, prompted by the FDA, resulted in a letter of non-approval.

Minaprine, a psychotropic drug, which was effective in the treatment of various depressive states. This drug was withdrawn because of the serious side effect. It was found, that minaprine inhibited the following enzymes, acetylcholinesterase and monoamine oxidase (MOA) A. It also binds to dopamine D1 and D2 receptors. Experiments on rodents also have revealed that minaprine suppressed the inhibitory effect of hydroxytryptamine (5-HT) on dopamine (DA) release via the inhibition of 5-HT binding at the 5-HT2 receptor on the nerve terminal.

Pivagabine [4-(2,2-dimethyl-1-oxopropylamino) butanoic acid] is a hydrophobic 4-aminobutyric acid derivative with neuromodulatory activity. Pharmacokinetic and toxicological evaluations showed that pivagabine penetrates the blood-brain barrier in rats, does not undergo metabolic transformation and exhibits a low toxicity after either single or repeated administration. Moreover, behavioral studies demonstrated that this compound prevented pentylenetetrazol- and bicuculline-induced convulsions in rats. Pivagabine was shown to improve performance on stress-related tests by reducing the anxiety-producing reactions to the various experimental settings. The marked antistress action of Pivagabine is mediated by antagonizing the effects of stress on GABA(A) receptor function and corticotropin-releasing factor concentrations in the brain, but not by altering the stress-induced increase in neurosteroid concentrations. Pivagabine treatment reduced the physical and mental fatigability of neurasthenia patients and increased their sense of well-being.

Oxitriptan is an aromatic amino acid with antidepressant activity. In vivo, oxitriptan is converted into 5-hydroxytryptamine (serotonin) as well as other neurotransmitters. Oxitriptan may exert its antidepressant activity via conversion to serotonin or directly by binding to serotonin receptors within the central nervous system. It is used as an antiepileptic and antidepressant. Oxitriptan is a worthwhile addition to the limited treatments available for obsessive-compulsive disorder and panic disorder, two psychiatric disorders which have previously been difficult to manage pharmacologically. Possible gastrointestinal side effects are: nausea, vomiting, abdominal pain, constipation or flatulence, which tend to disappear with continued treatment or, in any case, dose reduction. Other undesirable effects such as anorexia, xerostomia, tachycardia, extrasystoles, dizziness, headache, lightheadedness, tremor or myalgia may occur.

Nefazodone hydrochloride (trade name Serzone) is an antidepressant drug marketed by Bristol-Myers Squibb. Its sale was discontinued in 2003 in some countries, due to the small possibility of hepatic (liver) injury, which could lead to the need for a liver transplant, or even death. The incidence of severe liver damage is approximately 1 in 250,000 to 300,000 patient-years. On May 20, 2004, Bristol-Myers Squibb discontinued the sale of Serzone in the United States. Within the serotonergic system, nefazodone acts as an antagonist at type 2 serotonin (5-HT2) post-synaptic receptors and, like fluoxetine-type antidepressants, inhibits pre-synaptic serotonin (5-HT) reuptake. These mechanisms increase the amount of serotonin available to interact with 5-HT receptors. Within the noradrenergic system, nefazodone inhibits norepinephrine uptake minimally. Nefazodone also antagonizes alpha(1)-adrenergic receptors, producing sedation, muscle relaxation, and a variety of cardiovascular effects. Nefazodone's affinity for benzodiazepine, cholinergic, dopaminergic, histaminic, and beta or alpha(2)-adrenergic receptors is not significant.