Mephedrone (4-methylmethcathinone) is a β-ketoamphetamine belonging to the family of synthetic cathinones, an emerging class of designer drugs known for their hallucinogenic and psychostimulant properties as well as for their abuse potential. Mephedrone is a stimulant of dopamine (DA) release and blocks its reuptake through its interaction with the dopamine transporter. Furthermore, it has some affinity for various 5-hydroxytryptamine (5-HT) receptor subtypes. Neurotoxic effect of mephedrone on 5-HT and DA systems remains controversial. Although some studies in animal models reported no damage to DA nerve endings in the striatum and no significant changes in brain monoamine levels, some others suggested a rapid reduction in 5-HT and DA transporter function. Persistent serotonergic deficits were observed after binge like treatment in a warm environment and in both serotonergic and dopaminergic nerve endings at high ambient temperature. Oxidative stress cytotoxicity and an increase in frontal cortex lipid peroxidation were also reported. Despite the re-classification of mephedrone as a Class B restricted substance by the United Kingdom and restrictive legislation by the United States, international policy regarding mephedrone control is still developing and interest in synthetic amphetamine-like drugs could drive the development of future mephedrone analogues.

Parafluorofentanyl is a selective mu-opioid agonist, an analog of fentanyl, developed by Janssen. The drug was not developed for human use but is produced and abused illegally.

Norbolethone is a 19-nor anabolic steroid first synthesized in 1966. During the 1960s it was administered to humans in efficacy studies concerned with short stature and underweight conditions. It has never been reported by doping control laboratories prior to 2001. Norbolethone matches the description for what is described as a "designer steroid. " In fact, Norbolethone was given in clinical trials over 30 years ago and never given the green light. No supply was ever manufactured, and no test was ever developed to detect this substance, yet ironically, it was suspected of being used in the 2000 Olympics based on blood and urine assays done by the IOC. Norbolethone was used in the treatment of idiopathic underweight, prevention of indomethacin-induced intestinal ulcers.

Meclonazepam (Ro11-3128 or 3-methylclonazepam) is a benzodiazepine derivative. It exerts anxiolytic activity. Meclonazepam demonstrated anti-schistosomal action, it causes spastic paralysis, calcium influx and tegumental disruption in the parasites. Contracturant effect of meclonazepam is not a result of its binding to the worm benzodiazepine binding sites.

HU-308 ([(1R,2R,5R)-2-[2,6-dimethoxy-4-(2-methyloctan-2-yl)phenyl]-7,7-dimethyl-4-bicyclo[3.1.1]hept-3-enyl]methanol) is a potent, selective agonist for the CB2 receptor. The synthesis and characterization took place in the laboratory of Prof. Mechoulam at the Hebrew University of Jerusalem in the late 1990s. It has analgesic effects, promotes proliferation of neural stem cells,[3] and protects both liver and blood vessel tissues against oxidative stress via inhibition of TNF-α. In vivo, HU-308 has hypotensive, analgesic, and anti-inflammatory activities in mice that can be reversed by the CB2 receptor antagonist SR 144528 but not the CB1 receptor antagonist rimonabant. Pretreatment of mice with HU-308 decreases the I/R-induced tissue damage, inflammatory cell infiltration, tissue, and serum TNF-α, MIP-1, and MIP-2 levels, tissue lipid peroxidation, and apoptosis. HU-308 increases proliferation of HT29 colon cancer cells and growth of tumors in an HT29 mouse xenograft model. The physiological and toxicological properties of this compound have not been evaluated in humans.

Clonitazene is a synthetic opioid analgesic, structurally related to etonitazene. In the USA clonitazene is a schedule I narcotic controlled substance.

Etaqualone (Aolan, Athinazone) is an analog of the hypnotic methaqualone, a non-barbiturate sedative it was developed and marked in France. Etaqualone possesses sedative and hypnotic properties and was used to treat insomnia resulting from its agonist activity at the β subtype of the GABAa receptor.

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.