Spiramide (AMI-193) is a spiperone derivative, a selective 5-HT2A, (Ki = 2 nM) 5-HT1A (Ki = 50 nM), and D2 receptor (Ki = 3 nM) antagonist, with negligible affinity for the 5-HT2C receptor (Ki = 4300 nM). The ability of Spiramide to serve as a functional 5-HT2A antagonist in behavioral studies was demonstrated through studies in which Spiramide blocked the discriminative - stimulus effects of the 5HT2A agonist 1-(2,5-dimethoxy-4-methylphenyl)-2-aminopropane (DOM).

Spiroxatrine is a drug which acts as a selective antagonist at both the 5-HT1A receptor and the α2 adrenergic receptor. Spiroxatrine was identified as a moderately potent but non-selective agonist at the human nociceptin/orphanin FQ receptor, ORL1

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.

Norfentanyl is a major urinary metabolite of a potent, synthetic narcotic analgesic fentanyl.

Spiperone (Spiroperidol; brand name: Spiropitan (JP)) is a typical antipsychotic and research chemical belonging to the butyrophenone chemical class. Spiperone is selective D2 dopamine receptor antagonist; α1B-adrenoceptor antagonist; mixed 5-HT2A/5-HT1 serotonin receptor antagonist. Additionally, spiperone was identified by compound screening to be an activator of Ca2+ activated Cl− channels (CaCCs), thus a potential target for therapy of cystic fibrosis. Spiperone is widely used as a pharmacological tool for studying neurotransmitter receptors.

Norfentanyl is a major urinary metabolite of a potent, synthetic narcotic analgesic fentanyl.

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.