Vinepidine, a derivative of vincristine participated in clinical trials as an antineoplastic agent. As a result, the extreme neuromuscular toxicity was observed, that is why this study was discontinued.

Xorphanol (also known as TR5379M) is a full κ-opioid receptor agonist and is a partial agonist at μ opioid receptor. Clinically, xorphanol was studied as an orally active analgesic that provided effective pain relief but showed low physical dependence liability. Further development of this drug was discontinued.

Proxorphan is a N-substituted 6-oxamorphinane patented by American pharmaceutical company Bristol-Myers Co. as opioid analgesic and antitussive drug. Proxorphan acts as a κ-opioid receptor partial agonist and to a lesser extent as a μ-opioid receptor partial agonist.

Vinleurosine is a vinca alkaloid found in species of Catharanthus. This compound was studied as an anticancer agent and participated in clinical trials. However, the drug was more toxic and unpredictable in effect in comparison with vinblastine. Its further development was discontinued.

Coniine is a neurotoxic piperidine alkaloid found in poison hemlock (Conium maculatum L.). Coniine which is considered to be racemic mixture first described by Gieseke in 1827; von Hoffman confirmed the structure in 1881; Ladenburg perfermed synthesis in 1886. Coniine enantiomers are nicotinic acetylcholine receptor (nAChR) agonists. The relative potencies of these enantiomers on TE-671 cells expressing human fetal nicotinic neuromuscular receptors had the rank order of (-)-coniine > (+/-)-coniine > (+)-coniine. The rank order potency in SH-SY5Y cells which predominately express autonomic nAChRs was: (-)-coniine>(+)-coniine> (+/-)-coniine.

Gramine (aka donaxine) is a naturally occurring indole alkaloid that can be found in several plant species. It is toxic to many organisms and may be a natural defense mechanism for these plants. Gramine has been found to act as an agonist of the adiponectin receptor 1 (AdipoR1) which plays an important role in the suppression of metabolic disorders that can result in type 2 diabetes, obesity, and atherosclerosis.

Anabasine, a tobacco alkaloid, was used as a biomarker of active tobacco use. Anabasine is a selective alpha7-nicotinic acetylcholine receptor agonist. Anabasine antagonized MK-801-elicited mouse popping behavior, an animal model of schizophrenia.

Coniine is a neurotoxic piperidine alkaloid found in poison hemlock (Conium maculatum L.). Coniine which is considered to be racemic mixture first described by Gieseke in 1827; von Hoffman confirmed the structure in 1881; Ladenburg perfermed synthesis in 1886. Coniine enantiomers are nicotinic acetylcholine receptor (nAChR) agonists. The relative potencies of these enantiomers on TE-671 cells expressing human fetal nicotinic neuromuscular receptors had the rank order of (-)-coniine > (+/-)-coniine > (+)-coniine. The rank order potency in SH-SY5Y cells which predominately express autonomic nAChRs was: (-)-coniine>(+)-coniine> (+/-)-coniine.

Aniledrine is a narcotic pain reliver. The drug was prescribed as an analgesic in anaesthesia (Leritine brand name), however, it is no longer available on the market. Although the exact mechanism is not fully understood, aniledrine appears to elicit its action by binding to endorphine receptors in CNS.

Propoxyphene is a centrally acting opiate analgesic. Propoxyphene is an odorless, freely soluble in water, white crystalline powder with a bitter taste. In vitro studies demonstrated propoxyphene and the metabolite norpropoxyphene inhibit sodium channels (local anesthetic effect) with norpropoxyphene being approximately 2 fold more potent than propoxyphene and propoxyphene approximately 10 fold more potent than lidocaine. Propoxyphene and norpropoxyphene inhibit the voltage-gated potassium current carried by cardiac rapidly activating delayed rectifier (hERG) channels with approximately equal potency. It is unclear if the effects on ion channels occur within therapeutic dose range. Propoxyphene is indicated for the relief of mild to moderate pain.