- γ-Aminobutyric acid (GABA)
- Glutamic acid (glutamate)
Racetams, also sometimes known simply as pyrrolidones, [1] are a class of drugs that share a pyrrolidone nucleus. [2] [3] [4] Many, but not all, specifically have a 2-oxo-1-pyrrolidine acetamide (piracetam) nucleus. Some racetams, such as piracetam, aniracetam, oxiracetam, pramiracetam, and phenylpiracetam, are considered nootropics. [5] Phenylpiracetam is also a stimulant. [2] Others, such as levetiracetam, brivaracetam, and seletracetam, are anticonvulsants. [6]
There is no universally accepted mechanism of action for racetams. Racetams generally show negligible affinity for common central nervous system receptors, but modulation of central neurotransmitters, including acetylcholine and glutamate, has been reported. Although aniracetam and nebracetam show some affinity for muscarinic acetylcholine receptors, only nefiracetam demonstrates nanomolar interactions with neurotransmitter receptors. Modification of membrane-located mechanisms of central signal transduction is another hypothesis. [3]
Like some ampakines, some racetams, such as piracetam and aniracetam, are positive allosteric modulators of the AMPA receptor. [7]
Racetams are understood to work by allosterically modulating glutamate receptors, specifically AMPA receptors, leading to Ca2+ influx that is excitatory. [8] Racetams are posited to enhance memory through interaction with glutamate receptors in the central nervous system.
Phenylpiracetam, unique among racetams in being a phenethylamine and stimulant, is an atypical dopamine reuptake inhibitor. [9] [10] [11] [12]
Anticonvulsant racetams, including levetiracetam, brivaracetam, and seletracetam, act as synaptic vesicle glycoprotein 2A (SV2A) ligands. [6] A newer analogue of these agents, padsevonil, is no longer a racetam itself but is much more potent in comparison and interacts with not only SV2A but also synaptic vesicle glycoprotein 2B (SV2B) and synaptic vesicle glycoprotein 2C (SV2C). [6]
Methylphenylpiracetam, a derivative of phenylpiracetam, is a positive allosteric modulator of the sigma σ1 receptor. [10] [13] [14] [15] It is currently the only racetam known to possess this action. [10]
In studies with aged rats, marked improvement has been observed in cognitive tasks in experimental groups given piracetam. Performance was further increased when piracetam was combined with choline. Evidence in studies with rats has indicated that the potency of piracetam is increased when administered with choline. [16]
Structure | Name |
---|---|
![]() | Piracetam |
![]() | Oxiracetam |
![]() | Phenylpiracetam / Fonturacetam |
![]() | Phenylpiracetam Hydrazide / Fonturacetam Hydrazide |
![]() | Aniracetam |
![]() | Pramiracetam |
![]() | Seletracetam |
![]() | Levetiracetam |
![]() | Coluracetam / BCI-540 |
![]() | Fasoracetam |
![]() | Brivaracetam |
![]() | Dimiracetam |
![]() | Methylphenylpiracetam / E1R |
![]() | Nebracetam |
![]() | Nefiracetam |
![]() | Omberacetam / Noopept |
![]() | Rolziracetam |
![]() | Cebaracetam |
Racetams are 2-pyrrolidone derivatives and may sometimes be referred to simply as pyrrolidones (2-oxopyrrolidines). [1] Many, but not all, specifically have a 2-oxo-1-pyrrolidine acetamide nucleus, which is the chemical structure of piracetam.
Racetams are cyclic derivatives of the inhibitory neurotransmitter γ-aminobutyric acid (GABA). [2] They are also structurally related to the endogenous cyclic amino acid pyroglutamic acid (pyroglutamate), a cyclic analogue of the endogenous excitatory neurotransmitter glutamic acid (glutamate). [3] [4]
Some agents included in the racetam family are not technically racetams themselves in terms of chemical structure and instead are closely related compounds. [17] They may be referred to as "racetam-like". [17] [2] These agents include aloracetam, molracetam, omberacetam (noopept), padsevonil, and tenilsetam. [17] [6] [18]
All racetams are schedule 4 substances in Australia under the Poisons Standard (February 2020). [19] A schedule 4 substance is classified as "Prescription Only Medicine, or Prescription Animal Remedy – Substances, the use or supply of which should be by or on the order of persons permitted by State or Territory legislation to prescribe and should be available from a pharmacist on prescription." [19]
Nootropics, colloquially brain supplements, smart drugs and cognitive enhancers, are natural, semisynthetic or synthetic compounds which purportedly improve cognitive functions, such as executive functions, attention or memory.
Piracetam is a drug that has efficacy in cognitive disorders, vertigo, cortical myoclonus, dyslexia, and sickle cell anemia; sources differ on its usefulness for dementia. Piracetam is sold as a medication in many European countries. Sale of piracetam is not illegal in the United States, although it is not regulated nor approved by the FDA, so it is legally sold for research use only.
Aniracetam, also known as N-anisoyl-2-pyrrolidinone, is a racetam which is sold in Europe as a prescription drug. It is not approved by the Food and Drug Administration for use in the United States as a prescription medication or dietary supplement. Despite the FDA's lack of approval, the drug is readily available over-the-counter in misbranded dietary supplements.
Oxiracetam is a nootropic drug of the racetam family and a very mild stimulant. Several studies suggest that the substance is safe even when high doses are consumed for a long period of time. However, the mechanism of action of the racetam drug family is still a matter of research. Oxiracetam is not approved by Food and Drug Administration for any medical use in the United States.
Nefiracetam is a nootropic drug of the racetam family. Preliminary research suggests that it may possess certain antidementia properties in rats.
Nebracetam is an investigational drug of the racetam family that is a M1 acetylcholine receptor agonist in rats. Based on a human leukemic T cell experiment in 1991, it is believed to act as an agonist for human M1-muscarinic receptors. It is also believed to act as a nootropic, like many other racetam drugs. A chemoenzymatic method of synthesis was reported in 2008. As of 2023, human trials have not yet been conducted.
The dopamine transporter is a membrane-spanning protein coded for in humans by the SLC6A3 gene, that pumps the neurotransmitter dopamine out of the synaptic cleft back into cytosol. In the cytosol, other transporters sequester the dopamine into vesicles for storage and later release. Dopamine reuptake via DAT provides the primary mechanism through which dopamine is cleared from synapses, although there may be an exception in the prefrontal cortex, where evidence points to a possibly larger role of the norepinephrine transporter.
Phenylpiracetam, also known as fonturacetam and sold under the brand names Phenotropil, Actitropil, and Carphedon among others, is a stimulant and nootropic medication used in Russia and certain other Eastern European countries in the treatment of cerebrovascular deficiency, depression, apathy, and attention, and memory problems, among other indications. It is also used in Russian cosmonauts to improve physical, mental, and cognitive abilities. The drug is taken by mouth.
Dopaminergic means "related to dopamine", a common neurotransmitter. Dopaminergic substances or actions increase dopamine-related activity in the brain.
Mesocarb, sold under the brand name Sidnocarb or Sydnocarb and known by the developmental code name MLR-1017, is a psychostimulant medication which has been used in the treatment of psychiatric disorders and for a number of other indications in the Soviet Union and Russia. It is currently under development for the treatment of Parkinson's disease and sleep disorders. It is taken by mouth.
Seletracetam is a pyrrolidone-derived drug of the racetam family that is structurally related to levetiracetam. It was under development by UCB Pharmaceuticals as a more potent and effective anticonvulsant drug to replace levetiracetam but its development has been halted.
Cyclothiazide, sometimes abbreviated CTZ, is a benzothiadiazide (thiazide) diuretic and antihypertensive that was originally introduced in the United States in 1963 by Eli Lilly and was subsequently also marketed in Europe and Japan. Related drugs include diazoxide, hydrochlorothiazide, and chlorothiazide.
A eugeroic, or eugregoric, also known as a vigilance-promoting agent, is a type of drug that increases vigilance. The term has been used inconsistently and in multiple ways in the scientific literature, either to refer specifically to modafinil-type wakefulness-promoting agents or to refer to wakefulness-promoting agents generally. It was first introduced in the French literature in 1987 as a descriptor for modafinil-like wakefulness-promoting drugs and for purposes of distinguishing such drugs from psychostimulants. However, the term "eugeroic" has not been widely adopted in the literature, and instead the term "wakefulness-promoting agent" has been more widely used, both for modafinil-type drugs and other agents.
Sunifiram is an experimental drug which has antiamnesic effects in animal studies and with significantly higher potency than piracetam. Sunifiram is a molecular simplification of unifiram (DM-232). Another analogue is sapunifiram (MN-19). As of 2016, sunifiram had not been subjected to toxicology testing, nor to any human clinical trials, and is not approved for use anywhere in the world.
Unifiram is an experimental drug. that has antiamnesic and other effects in animal studies with far greater potency than piracetam. A number of related compounds are known, such as sunifiram (DM-235) and sapunifiram (MN-19). Unifiram has two enantiomers, with the dextro form being the more active isomer. It has been shown to reduce the duration of hypnosis induced by pentobarbital, without impairing motor coordination. As of 2015, no formal human studies with unifiram have been conducted. Unifiram is not patented and, despite the lack of human and long-term toxicity studies, it is commonly sold online.
A wakefulness-promoting agent (WPA), or wake-promoting agent, is a drug that increases wakefulness and arousal. They are similar to but distinct from psychostimulants, which not only promote wakefulness but also produce other more overt central nervous system effects, such as improved mood, energy, and motivation. Wakefulness-promoting agents are used to treat narcolepsy and hypersomnia as well as to promote wakefulness and increase performance in healthy people.
Methylphenylpiracetam is a derivative of piracetam and a positive allosteric modulator of the sigma-1 receptor. It differs from phenylpiracetam by having a methyl group.
MRZ-9547, also known as (R)-phenylpiracetam, (R)-phenotropil, or (R)-fonturacetam, is a selective dopamine reuptake inhibitor (IC50Tooltip half-maximal inhibitory concentration = 14.5 μM) that was developed by Merz Pharma. It is the (R)-enantiomer of the racetam and nootropic phenylpiracetam (phenotropil; fonturacetam).
Armesocarb (developmental code name MLR-1019), also known as (R)-mesocarb or L-mesocarb, is a selective atypical dopamine reuptake inhibitor (DRI). It is currently under development for the treatment of Parkinson's disease and sleep disorders.
The racetams have different activities [e.g., phenylpiracetam is a stimulant developed and marketed in Russia, piracetam is a nootropic, and levetiracetam is widely used as an anticonvulsant (Figure 17)].
Phenylpiracetam was originally designed as a nootropic drug for the sustenance and improvement of the physical condition and cognition abilities of Soviet space crews.2 Later, especially during the last decade, phenylpiracetam was introduced into general clinical practice in Russia and in some Eastern European countries. The possible target receptors and mechanisms for the acute activity of this drug remained unclear, until very recently it was found that (R)-phenylpiracetam (5) (MRZ-9547) is a selective dopamine transporter inhibitor that moderately stimulates striatal dopamine release.19
Here, we tested the effects of MRZ-9547 [...], and its l-enantiomer MRZ-9546 on effort-related decision making in rats. The racemic form of these compounds referred to as phenotropil has been shown to stimulate motor activity in rats (Zvejniece et al., 2011) and enhance physical capacity and cognition in humans (Malykh and Sadaie, 2010). [...] MRZ-9547 turned out to be a DAT inhibitor as shown by displacement of binding of [125I] RTI-55 (IC50 = 4.82 ± 0.05 μM, n=3) to human recombinant DAT expressed in CHO-K1 cells and inhibition of DA uptake (IC50 = 14.5 ± 1.6 μM, n=2) in functional assays in the same cells. It inhibited norepinephrine transporter (NET) with an IC50 of 182 μM (one experiment in duplicate). The potencies for the l-enantiomer MRZ-9546 were as follows: DAT binding (Ki = 34.8 ± 14.8 μM, n=3), DAT function (IC50 = 65.5 ± 8.3 μM, n=2) and NET function (IC50 = 667 μM, one experiment performed in duplicate).
In a study performed by Sommer et al. (2014), healthy rats treated with the selective dopamine transport (DAT) inhibitor MRZ-9547 (Fig. 1) chose high effort, high reward more often than their untreated matched controls. Unlike similar studies, however, depressive symptoms were not induced before treatment; rather, baseline healthy controls were compared to healthy rats treated with MRZ-9547. [...] In one study, the selective DAT inhibitor MRZ-9547 increased the number of lever presses more than untreated controls (Sommer et al., 2014). The investigators concluded that such effort-based "decision making in rodents could provide an animal model for motivational dysfunctions related to effort expenditure such as fatigue, e.g. in Parkinson's disease or major depression." Based upon the findings with MRZ-9547, they suggested that this drug mechanism might be a valuable therapeutic entity for fatigue in neurological and neuropsychiatric disorders. [...] A high effort bias been reported with bupropion (Randall et al., 2015), lisdexamfetamine (Yohn etal., 2016e), and the DA uptake blockers MRZ-9547 (Sommer et al., 2014), PRX-14040 (Fig. 1) (Yohn et al., 2016d) and GBR12909 (Fig. 1) (Yohn et al., 2016c).
The R-configuration enantiomers of methylphenylpiracetam are more active positive allosteric modulators of Sigma-1 receptor than S-configuration enantiomers.
Many of the products are based on a group of compounds known collectively as racetams or 'racetam-like' substances. [...] In addition, three substances that do not strictly meet the racetam definition (due to lack of a 2-pyrrolidone ring) are typically described as being part of the racetam family. These are aloracetam, molracetam and noopept.