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".

RP-67580 selectively inhibits the binding of substance-P to Neurokinin Receptor-1 and does not show meaningful antagonistic activity against NK2 and NK3. Preclinical trials had been conducted and discontinued in France for the potential treatment of inflammation and pain. RP-67580 has not been used in human trials.

7-Nitroindazole (aka 7-NI) is an experimental small molecule that acts as a selective inhibitor of neuronal nitric oxide synthase, which normally converts arginine to citrulline and nitric oxide (NO) in neuronal tissues. It has been investigated for potential use as an anti-nociceptive compound and as a means of mitigating neurodegenerative damage.

Dimethocaine (DMC, larocaine), a synthetic derivative of cocaine, is a widely distributed "legal high" consumed as a "new psychoactive substance" (NPS), originally was used in the 1930s as an anesthetic, primarily in dentistry, ophthalmology, and otolaryngology. This drug completely inhibits dopamine transporter and has had the potential for abuse. Dimethocaine is intended for forensic and research purposes.

GR79236 is an adenosine A1 receptor agonist, which possesses cardiovascular and antilipolytic properties. GR79236 was studied in model animals for the treatment of diabetic ketoacidosis and in patients for pain relief. However, these studies were discontinued. In addition, analgesic efficacy of GR79236 was investigated in the dental pain model. Nevertheless, there was no evidence of efficacy of GR79236. A higher dose of GR79236 might have been effective or that was suggested, that intravenous administration of that drug did not achieve appropriate concentrations in the brain or peripheral nerves.

1-(5-isoquinolinylsulfonyl)-2-methylpiperazine (H-7) is an inhibitor of cAMP-dependent, cGMP-dependent, and Ca2+-phospholipid-dependent (protein kinase C) protein kinases at roughly equal concentrations. It is widely used to study protein kinase signaling both in vitro and in vivo.

AZD-9272 is an orally bioavailable and brain-penetrant potent and selective mGluR5 negative allosteric modulator. It exhibits high selectivity for mGluR5 over other mGlu receptors. It had been in phase I clinical trials for the treatment of gastroesophageal reflux disease and neuropathic pain. Single doses of the centrally acting mGluR5-antagonist AZD-9272 did not reduce C-fibre evoked pain, central sensitization or flare reaction in the study aimed to investigate its effect on electrically induced pain, central sensitization and axon reflex flare.

11-NOR-9-CARBOXY-DELTA9-TETRAHYDROCANNABINOL (THC-COOH) is the main the non-psychoactive metabolite of Delta9-Tetrahydrocannabinol. Being most abundant in bodily fluids, it has become an established marker of cannabis consumption in forensic, clinical and environmental analyses. Among the cannabinoids tested as potential inhibitors of the drug efflux transporter P-glycoprotein (Pgp), which is responsible for the multidrug-resistance of a tumour and normal cells, THC-COOH behaved as a substrate and was the most active in stimulating Pgp-dependent ATPase. It displayed analgesic and anti-inflammatory properties apparently by inhibiting cyclooxygenase and 5-lipoxygenase activities. THC-COOH was not an anxiolytic or anxiogenic drug but abolished the anxiogenic behavioral effect of Delta9-Tetrahydrocannabinol.

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.

Umbelliferone is a natural product of the coumarin family which can be found in many different plant species. It absorbs ultraviolet light strongly at several wavelengths and is used in sunscreens. It has also been reported to have antioxidant, anti-inflammatory, and anti-nocioceptive properties.