A sulfide ion is composed of a lone sulfur atom. Its charge is negative two, giving sulfides this formula: S^2-. Sulfide is a strong base, so solutions of sulfide in water are basic, due to hydrolysis. One well-known ionic compound with a sulfide ion is H_2S. The infamous rotten-egg smell often associated with sulfur originates from this compound. Sodium sulfide nonahydrate is used in the formation of surface functionalized cadmium sulfide quantum dots.

AstraZeneca (formerly Astra) is developing robalzotan (NAD-299, AZD-7371), a 5-HT1A antagonist, for the potential treatment of depression and anxiety. The compound has entered phase II trials but was discontinued. Then it investigated for the treatment of irritable bowel syndrome, but the study was prematurely terminated. The same final has expected the development of robalzotan in phase II to treat overactive bladder, this investigation was terminated in July 2005.

Carnosol is an ortho-diphenolic diterpene with an abietane carbon skeleton with hydroxyl groups at positions C-11 and C-12 and a lactone moiety across the B ring. Carnosol is the product of oxidative degradation of carnosic acid. Carnosol is a naturally occurring phytopolyphenol found in rosemary that functions as an antioxidant, antimicrobial, and anticarcinogen. Carnosol has been shown to inhibit inductions of COX-2 by blocking PKC signaling. Carnosol is an inhibitor of AR and ER α. Several pre-clinical studies have suggested that carnosol selectively targets tumorigenic cell as opposed to non-tumorigenic cells and is safe and tolerable in animals. Carnosol has been shown to elicit chemopreventive effects by (1) blocking the bioactivation of carcinogens, (2) enhancing antioxidant and/or detoxification enzyme activities, (3) suppressing tumor-promoting inflammation, (4) inhibiting cell proliferation and inducing apoptosis selectively in cancer cells, and (5) blocking tumor angiogenesis and invasion.

Alpha methyltryptamine (AMT) is a tryptamine (indole ethylamine) derivative, which was developed in the 1960's by Upjohn with the intention for use as an antidepressant. It was used in Russia under the trade name Indopan for the treatment of Bipolar disorder and some form of depression, but currently not being produced because of serious side effects. In the 1990's, alpha-methyltryptamine became regulated as a Schedule I controlled substance in the United States. Pharmacologically, AMT has high affinity for the serotonin (5-HT) transporter, a number of 5-HT receptors, and potently inhibits reuptake of monoamines dopamine, 5-HT, and norepinephrine reuptake. AMT is also a monoamine oxidase A inhibitor that conceivably could contribute to its pharmacological effect and this drug also the most potent inhibitor of semicarbazide-sensitive amine oxidase (SSAO).

Talopram (Lu 3-010) is a selective inhibitor norepinephrine transporter belonging to the antidepressants of the thymoleptic group.

MPEP (2-methyl-6-(phenylethynyl)pyridine) was one of the first compounds found to act a selective antagonist for the metabotropic glutamate receptor subtype mGluR5. It was under development by Novartis in the late 1990's. MPEP was found to produce neuroprotective effects following acute brain injury in animals. MPEP was also found to have positive effects on animal models of depression, anxiety and morphine withdrawl.

Fonturacetam, also known as Phenylpiracetam, is marketed in Russia as Carphedon and Phenotropil. It is one of the first ever nootropic drugs and originally discovered in Russia. Fonturacetam acts on most neurotransmitter systems and has been used for its cognitive and physical enhancing properties, and also as an antidepressant.

Imiloxan is a highly selective alpha2B adrenoceptor antagonist and was developed for depression in the 1980s. In Phase 1 clinical trials imiloxan dosing led to hypersensitivity reactions; the molecule's development was discontinued.

Nelivaptan is a selective, orally active, non-peptide vasopressin receptor antagonist selective for the V1B subtype. It showed promise in preclinical animal models and advanced to phase II clinical trials for the treatment of anxiety and depression; however, in 2008, Sanofi-Aventis announced that further development of this drug had been halted.

Diclofensine is an antidepressant with equipotent inhibitive effects on the neuronal uptake of norepinephrine (NE), serotonin, and dopamine. It is devoid of monoamine-releasing or monoaminoxidase-inhibiting properties. Diclofensine was found to be an effective antidepressant in human trials, with relatively few side effects, but was ultimately dropped from clinical development.