Feprosidnine is a stimulant

Stimulant

Stimulants are psychoactive drugs which induce temporary improvements in either mental or physical function or both. Examples of these kinds of effects may include enhanced alertness, wakefulness, and locomotion, among others...

 drug which was developed in the USSR in the 1970s. It is structurally related to another Russian drug mesocarb

Mesocarb

Mesocarb is a stimulant drug which was developed in the USSR in the 1970s. It has been shown to act as a dopamine reuptake inhibitor which is slower acting but longer lasting and less neurotoxic than dextroamphetamine....

 but unlike mesocarb it has not been developed for medical use in humans.

Sydnophen has multiple mechanisms of action, the relative importance of which has not been clearly established. Effects on the body include cholinergic

Acetylcholine

The chemical compound acetylcholine is a neurotransmitter in both the peripheral nervous system and central nervous system in many organisms including humans...

, adrenergic, opioid

Opioid

An opioid is a psychoactive chemical that works by binding to opioid receptors, which are found principally in the central and peripheral nervous system and the gastrointestinal tract...

 and nitric oxide donating

Endothelium-derived relaxing factor

Endothelium-derived relaxing factor is produced and released by the endothelium to promote smooth muscle relaxation. The best-characterized is nitric oxide . Some sources equate EDRF and nitric oxide....

actions, all of which may contribute to its pharmacological effects to some extent.