L-760735 is a non-peptide substance P receptor (Neurokinin 1 (NK1) receptor) antagonist. It exerts anxiolytic, antidepressant and antinociceptive actions in animals. Merck was developing an L- 760735 as a potential antidepressant.

DB09173 (Butyrfentanyl or butyrylfentanyl) is a potent, short-acting mu opioid receptor agonist, and an analog of fentanyl, differing by only one methyl group. It has no approved medical indications but is being used for recreational purposes, with cases of fatal overdoses reported in Europe and the United States. Pre-clinical studies of butyrfentanyl are scarce; however, the few available studies suggest that butyrfentanyl is about 30 times less potent than fentanyl itself, and has significant antinociceptive properties, as demonstrated by the acetic acid writhing test in rodents. DB09173 is being abused for its opioid effects. As with other mu-opioid agonists, it can induce respiratory depression which may lead to death and numerous deaths have been reported. No studies of butyrfentanyl dependence or cross-dependence conducted in humans could be identified.

4-Piperidinol, 1-phenethyl-4-phenyl acetate (PEPAP) is a synthetic opioid discovered by Janssen in 1960. PEPAP is an analog of meperidine, it is abused and illegally sold on streets as a "synthetic heroin".

4-{2-[5-methyl-1-(naphthalen-2-yl)-1H-pyrazol-3-yloxy]ethyl}morpholine (S1RA, E-52862) is an 1-arylpyrazole class of sigma-1 receptor antagonist. Formalin-induced nociception (both phases), capsaicin-induced mechanical hypersensitivity and sciatic nerve injury-induced mechanical and thermal hypersensitivity were dose-dependently inhibited by systemic administration of S1RA. Occupancy of sigma-1 receptors in the CNS was significantly correlated with the antinociceptive effects. As a mechanistic correlate, electrophysiological recordings demonstrated that pharmacological antagonism of sigma-1 receptors attenuated the wind-up responses in spinal cords sensitized by repetitive nociceptive stimulation. Esteve is developing E 52862 for the treatment of several pain indications, including diabetic neuropathies, chemotherapy-induced neuropathic pain, postherpetic neuralgia, postoperative pain. Phase II development of this first-in-class agent is underway in Romania, Spain and Greece.

PHA-543613 was discovered by Pfizer and has been under development primarily as a potential treatment of schizophrenia. PHA-543613 acts as an agonist to the Neuronal acetylcholine receptor protein alpha-7 subunit. A single human trial was conducted in healthy human volunteers, but the compound has been studied extensively in rat models for schizophrenia as well as Parkinson's disease and Alzheimer's disease.

Chelerythrine is a kind of benzo[c] phenanthridine alkaloids, which is widely found in plant of Fumariaceae, Papaveraceae, Ranunculaceae and Rutaceae families. Chelerythrine is a potent and specific inhibitor of protein kinase C. In addition chelerythrine inhibits pro-survival protein Bcl(XL) thereby inducing apoptosis. It exerts antitumor properties.

(S)-ketorolac is the enantiomer of ketorolac, a nonsteroidal anti-inflammatory drug. (S)-ketorolac exhibited potent cyclooxygenase (COX1 and COX2) enzyme inhibition. (S)-ketorolac is considered to be active enantiomer of racemic ketorolac.

WIN 55212-2 is the synthetic cannabimimetic compound. It is a potent aminoalkylindole cannabinoid receptor agonist. WIN 55,212-2 increases expression of anti-oxidant Cu/Zn SOD and is able to prevent inflammation induced by Aβ1-42 in cultured astrocytes. It exerts neuroprotective and anti-inflammatory actions against Aβ damage through both CB₁ and CB₂ receptors. WIN 55212-2 attenuates hyperalgesia and allodynia in a rat model of neuropathic pain. In the clinical trial, it was revealed that WIN 55212-2, applied topically, decreases the intraocular pressure of human glaucoma resistant to conventional therapies within the first 30 min.

Norketamine is one of the major metabolites of Ketamine, which is routinely used as an anesthetic. Norketamine is a potent antagonist of the N-methyl-D-aspartate receptor and is believed to contribute to the analgesic effects of ketamine. In animal models, norketamine has been noted to increase the glomerular filtration rate by remodeling the cellular cytoskeleton, and it has been identified as having possible antidepressant effects.

Racemic phenibut (beta-phenyl-gamma-aminobutyric acid or 4-amino-3-phenylbutyric acid) is a neuropsychotropic drug that was discovered and introduced into clinical practice in Russia in the 1960s. In pharmacological tests of locomotor activity, antidepressant and pain effects, S-phenibut was inactive. In contrast, R-phenibut turned out to be two times more potent than racemic phenibut in most of the tests. Racemic phenibut and R-phenibut demonstrated an affinity for GABAB receptors, in contrast, S-phenibut was not able to bind receptors. Pharmacological activity of racemic phenibut relies on R-phenibut and this correlates to the binding affinity of enantiomers of phenibut to the GABAB receptor. Both S- and R-phenibut bind to the α2-δ subunit of voltage-dependent calcium channels and exert gabapentin-like anti-nociceptive effects. In addition S-isomer was found to be a substrate of gamma-aminobutyric acid aminotransferase, however, the R-isomer is a competitive inhibitor.