Clinical data | |
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Trade names | EPH |
Routes of administration | Insufflation, vaporized, intravenous, intramuscular, rectal, oral, sublingual |
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Pharmacokinetic data | |
Bioavailability | Variable |
Protein binding | Unknown |
Metabolism | Hepatic transesterification of prodrugs methylphenidate and ethanol |
Excretion | Urine, sweat |
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Chemical and physical data | |
Formula | C15H21NO2 |
Molar mass | 247.338 g·mol−1 |
3D model (JSmol) | |
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Ethylphenidate (EPH) is a psychostimulant and a close analog of methylphenidate.
Ethylphenidate acts as both a dopamine reuptake inhibitor and norepinephrine reuptake inhibitor, meaning it effectively boosts the levels of the norepinephrine and dopamine neurotransmitters in the brain, by binding to, and partially blocking the transporter proteins that normally remove those monoamines from the synaptic cleft.
However, considering the close similarities between ethylphenidate and methylphenidate and the fact that methylphenidate, like cocaine, actually does not primarily act as a "classical" reuptake inhibitor, but rather as an "inverse agonist at the DAT" (also called a "negative allosteric modulator at the DAT"), [3] it is at least very likely that ethylphenidate also primarily acts as an inverse DAT agonist instead of (or at least only secondarily) as a classical reuptake inhibitor (which could be called a "competitive antagonist at the DAT" using a similar terminology as "negative allosteric modulator at the DAT", which per definition means that its mechanism is non-competitive).
Ethylphenidate metabolizes into methylphenidate and ritalinic acid. [4]
Tiny amounts of ethylphenidate can be formed in vivo when ethanol and methylphenidate are coingested, via hepatic transesterification. [5] Ethylphenidate formation appears to be more common when large quantities of methylphenidate and alcohol are consumed at the same time, such as in non-medical use or overdose scenarios. [6] However, the transesterfication process of methylphenidate to ethylphenidate, as tested in mice liver, was dominant in the inactive (−)-enantiomer but showed a prolonged and increased maximal plasma concentration of the active (+)-enantiomer of methylphenidate. [7] Additionally, only a small percent of the consumed methylphenidate is converted to ethylphenidate. [5]
This carboxylesterase-dependent transesterification process is also known to occur when cocaine and alcohol are consumed together, forming cocaethylene. [8]
All available data on ethylphenidate's pharmacodynamics are drawn from studies conducted on rodents.[ citation needed ] Ethylphenidate is more selective to the dopamine transporter (DAT) than methylphenidate, having approximately the same efficacy as the parent compound, [7] but has significantly less activity on the norepinephrine transporter (NET). [9] Its dopaminergic pharmacodynamic profile is nearly identical to methylphenidate, and is primarily responsible for its euphoric and reinforcing effects. [10]
The eudysmic ratio for ethylphenidate is superior to that of methylphenidate. [7] [ failed verification ]
The following is ethylphenidate's binding profile in the mouse, alongside methylphenidate's. Figures for both the racemic and the dextrorotary enantiomers are given: [9]
Compound | Binding DAT | Binding NET | Uptake DA | Uptake NE |
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d-methylphenidate | 139 | 408 | 28 | 46 |
d-ethylphenidate | 276 | 2479 | 24 | 247 |
dl-methylphenidate | 105 | 1560 | 24 | 31 |
dl-ethylphenidate | 382 | 4824 | 82 | 408 |
Methylphenidate, sold under the brand names Ritalin and Concerta among others, is a central nervous system (CNS) stimulant used medically to treat attention deficit hyperactivity disorder (ADHD) and, to a lesser extent, narcolepsy. It is a primary medication for ADHD ; it may be taken by mouth or applied to the skin, and different formulations have varying durations of effect, commonly ranging from 2–4 hours.
Monoamine transporters (MATs) are proteins that function as integral plasma-membrane transporters to regulate concentrations of extracellular monoamine neurotransmitters. The three major classes are serotonin transporters (SERTs), dopamine transporters (DATs), and norepinephrine transporters (NETs) and are responsible for the reuptake of their associated amine neurotransmitters. MATs are located just outside the synaptic cleft (peri-synaptically), transporting monoamine transmitter overflow from the synaptic cleft back to the cytoplasm of the pre-synaptic neuron. MAT regulation generally occurs through protein phosphorylation and post-translational modification. Due to their significance in neuronal signaling, MATs are commonly associated with drugs used to treat mental disorders as well as recreational drugs. Compounds targeting MATs range from medications such as the wide variety of tricyclic antidepressants, selective serotonin reuptake inhibitors such as fluoxetine (Prozac) to stimulant medications such as methylphenidate (Ritalin) and amphetamine in its many forms and derivatives methamphetamine (Desoxyn) and lisdexamfetamine (Vyvanse). Furthermore, drugs such as MDMA and natural alkaloids such as cocaine exert their effects in part by their interaction with MATs, by blocking the transporters from mopping up dopamine, serotonin, and other neurotransmitters from the synapse.
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 dopamine not absorbed by the postsynaptic neuron is blocked from re-entering the presynaptic neuron. This results in increased extracellular concentrations of dopamine and increase in dopaminergic neurotransmission.
A norepinephrine reuptake inhibitor or noradrenaline reuptake inhibitor or adrenergic reuptake inhibitor (ARI), is a type of drug that acts as a reuptake inhibitor for the neurotransmitters norepinephrine (noradrenaline) and epinephrine (adrenaline) by blocking the action of the norepinephrine transporter (NET). This in turn leads to increased extracellular concentrations of norepinephrine and epinephrine and therefore can increase adrenergic neurotransmission.
Dexmethylphenidate, sold under the brand name Focalin among others, is a potent central nervous system (CNS) stimulant used to treat attention deficit hyperactivity disorder (ADHD) in those over the age of five years. It is taken by mouth. The immediate release formulation lasts up to five hours while the extended release formulation lasts up to twelve hours. It is the more active enantiomer of methylphenidate.
Cocaethylene (ethylbenzoylecgonine) is the ethyl ester of benzoylecgonine. It is structurally similar to cocaine, which is the methyl ester of benzoylecgonine. Cocaethylene is formed by the liver when cocaine and ethanol coexist in the blood. In 1885, cocaethylene was first synthesized, and in 1979, cocaethylene's side effects were discovered.
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.
Reuptake inhibitors (RIs) are a type of reuptake modulators. It is a drug that inhibits the plasmalemmal transporter-mediated reuptake of a neurotransmitter from the synapse into the pre-synaptic neuron. This leads to an increase in extracellular concentrations of the neurotransmitter and an increase in neurotransmission. Various drugs exert their psychological and physiological effects through reuptake inhibition, including many antidepressants and psychostimulants.
Difluoropine (O-620) is a stimulant drug synthesised from tropinone, which acts as a potent and selective dopamine reuptake inhibitor. Difluoropine is unique among the tropane-derived dopamine reuptake inhibitors in that the active stereoisomer is the (S) enantiomer rather than the (R) enantiomer, the opposite way round compared to natural cocaine. It is structurally related to benztropine and has similar anticholinergic and antihistamine effects in addition to its dopamine reuptake inhibitory action.
RTI(-4229)-112 is a synthetic stimulant drug from the phenyltropane family. In contrast to RTI-113, which is DAT selective, RTI-112 is a nonselective triple reuptake inhibitor.
A norepinephrine–dopamine reuptake inhibitor (NDRI) is a drug used for the treatment of clinical depression, attention deficit hyperactivity disorder (ADHD), narcolepsy, and the management of Parkinson's disease. The drug acts as a reuptake inhibitor for the neurotransmitters norepinephrine and dopamine by blocking the action of the norepinephrine transporter (NET) and the dopamine transporter (DAT), respectively. This in turn leads to increased extracellular concentrations of both norepinephrine and dopamine and, therefore, an increase in adrenergic and dopaminergic neurotransmission.
3,4-Dichloromethylphenidate is a stimulant drug related to methylphenidate. Dichloromethylphenidate is a potent psychostimulant that acts as both a dopamine reuptake inhibitor and norepinephrine reuptake inhibitor, meaning it effectively boosts the levels of the norepinephrine and dopamine neurotransmitters in the brain, by binding to, and partially blocking the transporter proteins that normally remove those monoamines from the synaptic cleft.
threo-4-Methylmethylphenidate (4-MeTMP) is a stimulant drug related to methylphenidate. It is slightly less potent than methylphenidate and has relatively low efficacy at blocking dopamine reuptake despite its high binding affinity, which led to its investigation as a possible substitute drug for treatment of stimulant abuse. On the other hand, several other simple ring-substituted derivatives of threo-methylphenidate such as the 4-fluoro and 3-chloro compounds are more potent than methylphenidate both in efficacy as dopamine reuptake inhibitors and in animal drug discrimination assays.
Methiopropamine (MPA) is an organic compound structurally related to methamphetamine. Originally reported in 1942, the molecule consists of a thiophene group with an alkyl amine substituent at the 2-position. It appeared for public sale in the UK in December 2010 as a "research chemical" or "legal high", recently branded as Blow. It has limited popularity as a recreational stimulant.
3,4-Dimethylmethcathinone (3,4-DMMC) is a stimulant drug first reported in 2010 as a designer drug analogue of mephedrone, apparently produced in response to the banning of mephedrone, following its widespread abuse in many countries in Europe and around the world. 3,4-DMMC has been seized as a designer drug in Australia. In vitro, 3,4-DMMC was shown to be a monoamine transporter substrate that potently inhibits norepinephrine and serotonin reuptake, and to a lesser extent dopamine reuptake.
A serotonin–dopamine reuptake inhibitor (SDRI) is a type of drug which acts as a reuptake inhibitor of the monoamine neurotransmitters serotonin and dopamine by blocking the actions of the serotonin transporter (SERT) and dopamine transporter (DAT), respectively. This in turn leads to increased extracellular concentrations of serotonin and dopamine, and, therefore, an increase in serotonergic and dopaminergic neurotransmission.
A monoamine reuptake inhibitor (MRI) is a drug that acts as a reuptake inhibitor of one or more of the three major monoamine neurotransmitters serotonin, norepinephrine, and dopamine by blocking the action of one or more of the respective monoamine transporters (MATs), which include the serotonin transporter (SERT), norepinephrine transporter (NET), and dopamine transporter (DAT). This in turn results in an increase in the synaptic concentrations of one or more of these neurotransmitters and therefore an increase in monoaminergic neurotransmission.
1-(3-Chlorophenyl)-4-(2-phenylethyl)piperazine (3C-PEP) is a designer drug of the piperazine class of chemical substances. 3C-PEP is related to meta-cholorophenylpiperazine (mCPP) and phenethylamine that can be thought of as mCPP having a phenylethyl group attached to the nitrogen atom at its 4-position. It was first described in 1994 in a patent disclosing a series of piperazine compounds as sigma receptor ligands. Later, it was discovered to be a highly potent dopamine reuptake inhibitor.
4-Fluoromethylphenidate is a stimulant drug that acts as a higher potency dopamine reuptake inhibitor than the closely related methylphenidate.
1-Methyl-3-propyl-4-(p-chlorophenyl)piperidine is a drug developed by a team led by Alan Kozikowski, which acts as a potent dopamine reuptake inhibitor, and was developed as a potential therapeutic agent for the treatment of cocaine addiction. As with related compounds such as nocaine, it is a structurally simplified derivative of related phenyltropane compounds. Its activity at the serotonin and noradrenaline transporters has not been published, though most related 4-phenylpiperidine derivatives are relatively selective for inhibiting dopamine reuptake over the other monoamine neurotransmitters. While several of its isomers are active, the (3S,4S)-enantiomer is by far the most potent. The rearranged structural isomer 2-[1-(4-chlorophenyl)butyl]piperidine is also a potent inhibitor of dopamine reuptake.
In vivo experiments in animals demonstrate that cocaine's monoaminergic pharmacology is profoundly different from that of other prescribed monoamine reuptake inhibitors, with the exception of methylphenidate. These findings led us to conclude that the highly unusual stimulant profile of cocaine and related compounds, eg methylphenidate, is not mediated by monoamine reuptake inhibition alone. We describe the experimental findings which suggest cocaine serves as a negative allosteric modulator to alter the function of the dopamine reuptake transporter (DAT) and reverse its direction of transport. This results in a firing-dependent, retro-transport of dopamine into the synaptic cleft. [...] Because the physiological role of DAT is to remove dopamine from the synapse and the action of cocaine is the opposite of this, we have postulated that cocaine's effect is analogous to an inverse agonist.