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).
Pharmacology
Pharmacokinetics
Ethylphenidate metabolizes into methylphenidate and ritalinic acid.[4]
Tiny amounts of ethylphenidate can be formed in vivo when ethanol and methylphenidate are coingested, via hepatictransesterification.[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 percentage 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]
Pharmacodynamics
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 dopaminergicpharmacodynamic profile is nearly identical to methylphenidate, and is primarily responsible for its euphoric and reinforcing effects.[10]
The following is ethylphenidate's binding profile in the mouse, alongside methylphenidate's. Figures for both the racemic and the dextrorotaryenantiomers are given:[9]
Ethylphenidate is illegal in the Netherlands, as the Opium Law Lijst I covers it, as of April 27, 2018 [12]
Ethylphenidate is not explicitly controlled in the US as part of the Controlled Substances Act but it could possibly be considered an analog of a Schedule II substance (methylphenidate) under the Federal Analog Act if sold for human consumption.
In the United States, on September 22, 2023, the DEA filed a proposed rule for placement of Ethylphenidate into Schedule I status. Public commenting opened on September 22, 2023, and closed on November 21, 2023.[11]
Ethylphenidate is illegal in Sweden as of December 15, 2012.
Ethylphenidate is illegal to manufacture, distribute or import in the UK, as of 10 April 2015 it has been placed under a Temporary Class Drug Order which automatically places it in a Class-B-like category.[13] Though ordinarily the TCDO would only last 1 year, the ACMD reported that since its invocation prevalence of MPA had significantly decreased, and that it had been challenging to collect information about the drug. As a result of this, they requested that the TCDO be extended a further year from 26 June 2016.[14]
Ethylphenidate is illegal in Jersey under the Misuse of Drugs (Jersey) Law 1978.[15]
Australian state and federal legislation contains provisions that mean that analogues of controlled drugs are also covered by the legislation. Ethylphenidate would be an analogue of methylphenidate under this legislation.[16]
^Heal DJ, Gosden J, Smith SL (December 2014). "Dopamine reuptake transporter (DAT) "inverse agonism"--a novel hypothesis to explain the enigmatic pharmacology of cocaine". Neuropharmacology. 87: 19–40. doi:10.1016/j.neuropharm.2014.06.012. PMID24953830. S2CID4660652. 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.
^Negreira N, Erratico C, van Nuijs AL, Covaci A (January 2016). "Identification of in vitro metabolites of ethylphenidate by liquid chromatography coupled to quadrupole time-of-flight mass spectrometry". Journal of Pharmaceutical and Biomedical Analysis. 117 (5): 474–84. doi:10.1016/j.jpba.2015.09.029. hdl:10067/1301870151162165141. PMID26454340.
^ abMarkowitz JS, DeVane CL, Boulton DW, Nahas Z, Risch SC, Diamond F, Patrick KS (June 2000). "Ethylphenidate formation in human subjects after the administration of a single dose of methylphenidate and ethanol". Drug Metabolism and Disposition. 28 (6): 620–4. PMID10820132.
^Markowitz JS, Logan BK, Diamond F, Patrick KS (August 1999). "Detection of the novel metabolite ethylphenidate after methylphenidate overdose with alcohol coingestion". Journal of Clinical Psychopharmacology. 19 (4): 362–6. doi:10.1097/00004714-199908000-00013. PMID10440465.
^ abcPatrick KS, Williard RL, VanWert AL, Dowd JJ, Oatis JE, Middaugh LD (April 2005). "Synthesis and pharmacology of ethylphenidate enantiomers: the human transesterification metabolite of methylphenidate and ethanol". Journal of Medicinal Chemistry. 48 (8): 2876–81. doi:10.1021/jm0490989. PMID15828826.
^Bourland JA, Martin DK, Mayersohn M (December 1997). "Carboxylesterase-mediated transesterification of meperidine (Demerol) and methylphenidate (Ritalin) in the presence of [2H6]ethanol: preliminary in vitro findings using a rat liver preparation". Journal of Pharmaceutical Sciences. 86 (12): 1494–6. doi:10.1021/js970072x. PMID9423167.
^ abWilliard RL, Middaugh LD, Zhu HJ, Patrick KS (February 2007). "Methylphenidate and its ethanol transesterification metabolite ethylphenidate: brain disposition, monoamine transporters and motor activity". Behavioural Pharmacology. 18 (1): 39–51. doi:10.1097/FBP.0b013e3280143226. PMID17218796. S2CID20232871.
^"Opiumwet" [Opium Act]. Ministerie van Binnenlandse Zaken en Koninkrijksrelaties [Ministry of the Interior and Kingdom Relations] (in Dutch). Retrieved 30 January 2022.
^Parks C, McKeown D, Torrance HJ (December 2015). "A review of ethylphenidate in deaths in east and west Scotland". Forensic Science International. 257: 203–208. doi:10.1016/j.forsciint.2015.08.008. PMID26375622.
^"关于印发《非药用类麻醉药品和精神药品列管办法》的通知" (in Chinese). China Food and Drug Administration. 27 September 2015. Archived from the original on 1 October 2015. Retrieved 1 October 2015.