Mesocarb, sold under the brand name Sidnocarb or Sydnocarb and known by the developmental code name MLR-1017, is a

psychostimulant Stimulants (also known as central nervous system stimulants, or psychostimulants, or colloquially as uppers) are a class of drugs that increase alertness. They are used for various purposes, such as enhancing attention, motivation, cognition ...

medication Medication (also called medicament, medicine, pharmaceutical drug, medicinal product, medicinal drug or simply drug) is a drug used to medical diagnosis, diagnose, cure, treat, or preventive medicine, prevent disease. Drug therapy (pharmaco ...

which has been used in the treatment of

psychiatric disorder A mental disorder, also referred to as a mental illness, a mental health condition, or a psychiatric disability, is a behavioral or mental pattern that causes significant distress or impairment of personal functioning. A mental disorder is ...

s and for a number of other indications in the

Soviet Union The Union of Soviet Socialist Republics. (USSR), commonly known as the Soviet Union, was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 until Dissolution of the Soviet ...

and

Russia Russia, or the Russian Federation, is a country spanning Eastern Europe and North Asia. It is the list of countries and dependencies by area, largest country in the world, and extends across Time in Russia, eleven time zones, sharing Borders ...

. It is currently under development for the treatment of

Parkinson's disease Parkinson's disease (PD), or simply Parkinson's, is a neurodegenerative disease primarily of the central nervous system, affecting both motor system, motor and non-motor systems. Symptoms typically develop gradually and non-motor issues become ...

and

sleep disorder A sleep disorder, or somnipathy, is a medical disorder affecting an individual's sleep patterns, sometimes impacting physical, mental, social, and emotional functioning. Polysomnography and actigraphy are tests commonly ordered for diagnosing sle ...

s. It is taken

by mouth Oral administration is a route of administration whereby a substance is taken through the Human mouth, mouth, swallowed, and then processed via the digestive system. This is a common route of administration for many medications. Oral administ ...

. The drug is a selective

dopamine reuptake inhibitor A dopamine reuptake inhibitor (DRI) is a class of drug which acts as a reuptake inhibitor of the monoamine neurotransmitter dopamine by blocking the action of the dopamine transporter (DAT). Reuptake inhibition is achieved when extracellular dop ...

(DRI). It is an unusual and unique DRI, acting as a

negative allosteric modulator In pharmacology and biochemistry, allosteric modulators are a group of substances that bind to a receptor to change that receptor's response to stimuli. Some of them, like benzodiazepines or alcohol, function as psychoactive drugs. The site that a ...

and non-competitive inhibitor of the

dopamine transporter The dopamine transporter (DAT, also sodium-dependent dopamine transporter) is a membrane-spanning protein coded for in humans by the ''SLC6A3'' gene (also known as ''DAT1''), that pumps the neurotransmitter dopamine out of the synaptic cleft ba ...

(DAT). Chemically, mesocarb contains

amphetamine Amphetamine (contracted from Alpha and beta carbon, alpha-methylphenethylamine, methylphenethylamine) is a central nervous system (CNS) stimulant that is used in the treatment of attention deficit hyperactivity disorder (ADHD), narcolepsy, an ...

within its

structure A structure is an arrangement and organization of interrelated elements in a material object or system, or the object or system so organized. Material structures include man-made objects such as buildings and machines and natural objects such as ...

but has been modified and extended at the

amine In chemistry, amines (, ) are organic compounds that contain carbon-nitrogen bonds. Amines are formed when one or more hydrogen atoms in ammonia are replaced by alkyl or aryl groups. The nitrogen atom in an amine possesses a lone pair of elec ...

with a sydnone imine-containing moiety. Mesocarb was first described by 1971. It was used as a

pharmaceutical drug Medication (also called medicament, medicine, pharmaceutical drug, medicinal product, medicinal drug or simply drug) is a drug used to diagnose, cure, treat, or prevent disease. Drug therapy ( pharmacotherapy) is an important part of the ...

until 2008. In 2021, its nature as a DAT allosteric modulator was reported. As of February 2023, mesocarb was in phase 1

clinical trial Clinical trials are prospective biomedical or behavioral research studies on human subject research, human participants designed to answer specific questions about biomedical or behavioral interventions, including new treatments (such as novel v ...

s for Parkinson's disease. The active

enantiomer In chemistry, an enantiomer (Help:IPA/English, /ɪˈnænti.əmər, ɛ-, -oʊ-/ Help:Pronunciation respelling key, ''ih-NAN-tee-ə-mər''), also known as an optical isomer, antipode, or optical antipode, is one of a pair of molecular entities whi ...

, armesocarb, is also being developed.

Medical uses

Mesocarb was originally developed in the

in the 1970s for a variety of indications including

asthenia Weakness is a symptom of many different medical conditions. The causes are many and can be divided into conditions that have true or perceived muscle weakness. True muscle weakness is a primary symptom of a variety of skeletal muscle diseases, ...

apathy Apathy, also referred to as indifference, is a lack of feeling, emotion, interest, or concern about something. It is a state of indifference, or the suppression of emotions such as concern, excitement, motivation, or passion. An apathetic i ...

, adynamia, and some clinical aspects of depression and

schizophrenia Schizophrenia () is a mental disorder characterized variously by hallucinations (typically, Auditory hallucination#Schizophrenia, hearing voices), delusions, thought disorder, disorganized thinking and behavior, and Reduced affect display, f ...

. Mesocarb was used for counteracting the

sedative A sedative or tranquilliser is a substance that induces sedation by reducing irritability or Psychomotor agitation, excitement. They are central nervous system (CNS) Depressant, depressants and interact with brain activity, causing its decelera ...

effects of

benzodiazepine Benzodiazepines (BZD, BDZ, BZs), colloquially known as "benzos", are a class of central nervous system (CNS) depressant, depressant drugs whose core chemical structure is the fusion of a benzene ring and a diazepine ring. They are prescribed t ...

s, increasing workload capacity and

cardiovascular In vertebrates, the circulatory system is a system of organs that includes the heart, blood vessels, and blood which is circulated throughout the body. It includes the cardiovascular system, or vascular system, that consists of the heart a ...

function, treatment of

attention deficit hyperactivity disorder Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder characterised by symptoms of inattention, hyperactivity, impulsivity, and emotional dysregulation that are excessive and pervasive, impairing in multiple con ...

(ADHD) in children, as a

nootropic Nootropics ( or ) (colloquially brain supplements, smart drugs, cognitive enhancers, memory enhancers, or brain boosters) are chemical substances which purportedly improve cognitive functions, such as attention, memory, wakefulness, and self ...

, and as a drug to enhance resistance to extremely cold temperatures. It has also been reported to have

antidepressant Antidepressants are a class of medications used to treat major depressive disorder, anxiety disorders, chronic pain, and addiction. Common side effects of antidepressants include Xerostomia, dry mouth, weight gain, dizziness, headaches, akathi ...

and

anticonvulsant Anticonvulsants (also known as antiepileptic drugs, antiseizure drugs, or anti-seizure medications (ASM)) are a diverse group of pharmacological agents used in the treatment of epileptic seizures. Anticonvulsants are also used in the treatme ...

properties.

Available forms

Mesocarb was sold in

as 5mg

oral The word oral may refer to: Relating to the mouth * Relating to the mouth, the first portion of the alimentary canal that primarily receives food and liquid **Oral administration of medicines ** Oral examination (also known as an oral exam or ora ...

tablets under the brand name Sydnocarb.

Pharmacology

Pharmacodynamics

Mesocarb has been found to act as a selective

(DRI) by blocking the actions of the

(DAT), and lacks the dopamine release characteristic of stimulants such as

dextroamphetamine Dextroamphetamine (international nonproprietary name, INN: dexamfetamine) is a potent central nervous system (CNS) stimulant and enantiomer of amphetamine that is used in the treatment of attention deficit hyperactivity disorder (ADHD) and narc ...

. It was the most selective DAT inhibitor amongst an array of other DAT inhibitors to which it was compared and, in 2017, was reported as the most selective DAT inhibitor described to date. The affinities (K_i) of mesocarb at the human

monoamine transporter Monoamine transporters (MATs) are proteins that function as integral Cell membrane, plasma-membrane Neurotransmitter transporter, transporters to regulate concentrations of extracellular monoamine neurotransmitters. The three major classes are se ...

s ''

in vitro ''In vitro'' (meaning ''in glass'', or ''in the glass'') Research, studies are performed with Cell (biology), cells or biological molecules outside their normal biological context. Colloquially called "test-tube experiments", these studies in ...

'' have been reported to be 8.3nM for the

(DAT), 1,500nM for the

norepinephrine transporter The norepinephrine transporter (NET), also known as noradrenaline transporter (NAT), is a protein that in humans is encoded by the solute carrier family 6 member 2 (SLC6A2) gene. NET is a monoamine transporter and is responsible for the sodium ...

(NET) (181-fold lower than for the DAT), and >10,000nM for the

serotonin transporter The serotonin transporter (SERT or 5-HTT) also known as the sodium-dependent serotonin transporter and solute carrier family 6 member 4 is a protein that in humans is encoded by the SLC6A4 gene. SERT is a type of monoamine transporter protein t ...

(SERT) (>1,205-fold lower than for the DAT). The inhibitory potencies () of mesocarb at the human monoamine transporters ''in vitro'' have been reported to be 0.49 ± 0.14μM at the DAT, 34.9 ± 14.08μM at the NET (71-fold lower than for the DAT), and 494.9 ± 17.00μM at the SERT (1,010-fold lower than for the DAT). In 2021, it was discovered that mesocarb is not a conventional DRI but acts as a DAT

allosteric modulator In pharmacology and biochemistry, allosteric modulators are a group of substances that bind to a receptor to change that receptor's response to stimuli. Some of them, like benzodiazepines or alcohol, function as psychoactive drugs. The site that a ...

or non-competitive inhibitor. In accordance with its nature as an atypical DAT blocker, the drug has atypical effects relative to conventional DRIs. As an example, it shows greater

antiparkinsonian In the management of Parkinson's disease, due to the chronic nature of Parkinson's disease (PD), a broad-based program is needed that includes patient and family education, support-group services, general wellness maintenance, exercise, and nutr ...

activity relative to other DRIs in animals. Similarly to other DRIs, mesocarb has been found to possess

wakefulness-promoting 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 n ...

effects.

Pharmacokinetics

Hydroxylated In chemistry, hydroxylation refers to the installation of a hydroxyl group () into an organic compound. Hydroxylations generate alcohols and phenols, which are very common functional groups. Hydroxylation confers some degree of water-solubility ...

metabolite In biochemistry, a metabolite is an intermediate or end product of metabolism. The term is usually used for small molecules. Metabolites have various functions, including fuel, structure, signaling, stimulatory and inhibitory effects on enzymes, c ...

s can be detected in

urine Urine is a liquid by-product of metabolism in humans and many other animals. In placental mammals, urine flows from the Kidney (vertebrates), kidneys through the ureters to the urinary bladder and exits the urethra through the penile meatus (mal ...

for up to 10days after consumption. Mesocarb had erroneously been referred to as a

prodrug A prodrug is a pharmacologically inactive medication or compound that, after intake, is metabolized (i.e., converted within the body) into a pharmacologically active drug. Instead of administering a drug directly, a corresponding prodrug can be ...

. However, this was based on older literature that relied on

gas chromatography Gas chromatography (GC) is a common type of chromatography used in analytical chemistry for Separation process, separating and analyzing compounds that can be vaporized without Chemical decomposition, decomposition. Typical uses of GC include t ...

as an analytical method. Subsequently, with the advent of

mass spectroscopy Mass spectrometry (MS) is an analytical technique that is used to measure the mass-to-charge ratio of ions. The results are presented as a ''mass spectrum'', a plot of intensity as a function of the mass-to-charge ratio. Mass spectrometry is used ...

, it has been shown that presence of amphetamine in prior studies was an artifact of the gas chromatography method. More recent studies using mass spectroscopy show that negligible levels of amphetamine are released from mesocarb

metabolism Metabolism (, from ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run cellular processes; the co ...

Chemistry

Mesocarb, also known as 3-(β-phenylisopropyl)-''N''-phenylcarbamoylsydnonimine, is a

substituted phenethylamine Substituted phenethylamines (or simply phenethylamines) are a chemical class of organic compounds that are based upon the phenethylamine structure; the class is composed of all the derivative (chemistry), derivative compounds of phenethylamine ...

and

and a

mesoionic In chemistry, mesoionic compounds are one in which a heterocyclic structure is dipolar and where both the negative and the positive charges are delocalized. A completely uncharged structure cannot be written and mesoionic compounds cannot be repr ...

sydnone imine. It has the

backbone present, except that the ''R''_N has a complicated imine

side chain In organic chemistry and biochemistry, a side chain is a substituent, chemical group that is attached to a core part of the molecule called the "main chain" or backbone chain, backbone. The side chain is a hydrocarbon branching element of a mo ...

present. Whereas mesocarb (MLR-1017) is a

racemic mixture In chemistry, a racemic mixture or racemate () is a mixture that has equal amounts (50:50) of left- and right-handed enantiomers of a chiral molecule or salt. Racemic mixtures are rare in nature, but many compounds are produced industrially as r ...

, the

enantiopure In chemistry, an enantiomer ( /ɪˈnænti.əmər, ɛ-, -oʊ-/ ''ih-NAN-tee-ə-mər''), also known as an optical isomer, antipode, or optical antipode, is one of a pair of molecular entities which are mirror images of each other and non-superpos ...

levorotatory Optical rotation, also known as polarization rotation or circular birefringence, is the rotation of the orientation of the plane of polarization about the optical axis of linearly polarized light as it travels through certain materials. Circul ...

or (''R'')-

is known as armesocarb (MLR-1019). Armesocarb is described as the

active Active may refer to: Music * ''Active'' (album), a 1992 album by Casiopea * "Active" (song), a 2024 song by Asake and Travis Scott from Asake's album ''Lungu Boy'' * Active Records, a record label Ships * ''Active'' (ship), several com ...

enantiomer of mesocarb, whereas the (''S'')- or D-enantiomer is said to be virtually inactive. It is structurally related to feprosidnine (Sydnophen; 3-(α-methylphenylethyl)sydnone imine).

Synthesis

Feprosidnine (Sydnophen) is converted from the hydrochloride salt (1) into the freebase amine (2). This is then treated with phenylisocyanate (3).

History

Mesocarb was first described in the

scientific literature Scientific literature encompasses a vast body of academic papers that spans various disciplines within the natural and social sciences. It primarily consists of academic papers that present original empirical research and theoretical ...

by 1971. It is said to have been used as a

from 1971 until 2008. It was said to have been discontinued by its manufacturer in 2008 for business reasons unrelated to the drug itself.

Society and culture

Names

''Mesocarb'' is the generic name of the drug and its . It is also known by the synonym ''fensidnimine'' as well as by the brand names ''Sydnocarb'' and ''Synocarb''. The drug is additionally known by its developmental code name ''MLR-1017'' (for Parkinson's disease).

Status

Mesocarb is almost unknown in the western world and is neither used in medicine nor studied scientifically to any great extent outside of

and other countries in the former

. It has however been added to the list of drugs under international control and is a scheduled substance in most countries, despite its multiple therapeutic applications and reported lack of significant

abuse potential Substance misuse, also known as drug misuse or, in older vernacular, substance abuse, is the use of a drug in amounts or by methods that are harmful to the individual or others. It is a form of substance-related disorder, differing definitions ...

Research

Parkinson's disease

Mesocarb, has been under development for the treatment of

since 2016. As of February 2023, it is in phase 1

s for this indication. However, no recent development has been reported. Mesocarb's active enantiomer armesocarb is also under development.

References

{{Phenethylamines Antidepressants Antiparkinsonian agents Dopamine reuptake inhibitors Drugs in the Soviet Union Experimental drugs Imines Oxadiazoles Russian drugs Stimulants Substituted amphetamines Ureas Wakefulness-promoting agents Withdrawn drugs