Dexmethylphenidate

Dexmethylphenidate, sold under the brand name Focalin among others, is a medication used to treat attention deficit hyperactivity disorder (ADHD) in those over the age of 5 years.[2] If no benefit is seen after 4 weeks it is reasonable to discontinue its use.[2] It is taken by mouth.[2] The immediate release formulation lasts up to 5 hours while the extended release formulation lasts up to 12 hours.[3]

Dexmethylphenidate
Clinical data
Trade namesFocalin, Focalin XR, Attenade, others
Other namesd-threo-methylphenidate (D-TMP)
AHFS/Drugs.comMonograph
MedlinePlusa603014
License data
Pregnancy
category
  • US: C (Risk not ruled out) [1]
    Dependence
    liability    		Physical: None Psychological: High
    Routes of
    administration    		By mouth
    ATC code
    Legal status
    Legal status
    Pharmacokinetic data
    Bioavailability11–52%
    Protein binding30%
    MetabolismLiver
    Elimination half-life4 hours
    ExcretionKidney
    Identifiers
    CAS Number
    PubChem CID
    IUPHAR/BPS
    DrugBank
    ChemSpider
    UNII
    KEGG
    ChEBI
    ChEMBL
    CompTox Dashboard (EPA)
    Chemical and physical data
    FormulaC14H19NO2
    Molar mass233.311 g·mol−1
    3D model (JSmol)
     NY (what is this?)  (verify)

    Common side effects include abdominal pain, loss of appetite, and fever.[2] Serious side effects may include abuse, psychosis, sudden cardiac death, mania, anaphylaxis, seizures, and dangerously prolonged erection.[2] Safety during pregnancy and breastfeeding is unclear.[1] Dexmethylphenidate is a central nervous system (CNS) stimulant.[4][2] How it works in ADHD is unclear.[2] It is the more active enantiomer of methylphenidate.[2]

    Dexmethylphenidate was approved for medical use in the United States in 2001.[5] It is available as a generic medication.[2] The wholesale cost of a month supply in the United States is about US$8.[6] In 2017, it was the 189th most commonly prescribed medication in the United States, with more than three million prescriptions.[7][8] It is also available in Switzerland.[9]

    Medical uses

    Dexmethylphenidate is used as a treatment for ADHD, usually along with psychological, educational, behavioral or other forms of treatment. It is proposed that stimulants help ameliorate the symptoms of ADHD by making it easier for the user to concentrate, avoid distraction, and control behavior. Placebo-controlled trials have shown that once-daily dexmethylphenidate XR was effective and generally well tolerated.[4]

    Improvements in ADHD symptoms in children were significantly greater for dexmethylphenidate XR versus placebo.[4] It also showed greater efficacy than osmotic controlled-release oral delivery system (OROS) methylphenidate over the first half of the laboratory classroom day but assessments late in the day favoured OROS methylphenidate.[4]

    Contraindications

    Methylphenidate is contraindicated for individuals using monoamine oxidase inhibitors (e.g., phenelzine, and tranylcypromine), or individuals with agitation, tics, glaucoma, or a hypersensitivity to any ingredients contained in methylphenidate pharmaceuticals.[10]

    The US Food and Drug Administration (FDA) gives methylphenidate a pregnancy category of C, and women are advised to only use the drug if the benefits outweigh the potential risks.[11] Not enough human studies have been conducted to conclusively demonstrate an effect of methylphenidate on fetal development.[12] In 2018, a review concluded that it has not been teratogenic in rats and rabbits, and that it "is not a major human teratogen".[13]

    Adverse effects

    Products containing dexmethylphenidate have a side effect profile comparable to those containing methylphenidate.[14]

    Addiction experts in psychiatry, chemistry, pharmacology, forensic science, epidemiology, and the police and legal services engaged in delphic analysis regarding 20 popular recreational drugs. Methylphenidate was ranked 13th in dependence, 12th in physical harm, and 18th in social harm.[15]

    The most common adverse effects include appetite loss, dry mouth, anxiety/nervousness, nausea, and insomnia. Gastrointestinal adverse effects may include abdominal pain and weight loss. Nervous system adverse effects may include akathisia (agitation/restlessness), irritability, dyskinesia (tics), lethargy (drowsiness/fatigue), and dizziness. Cardiac adverse effects may include palpitations, changes in blood pressure and heart rate (typically mild), and tachycardia (rapid heart rate).[16] Ophthalmologic adverse effects may include blurred vision and dry eyes, with less frequent reports of diplopia and mydriasis.[17]

    There is some evidence of mild reductions in height with prolonged treatment in children.[18] This has been estimated at 1 centimetre (0.4 in) or less per year during the first three years with a total decrease of 3 centimetres (1.2 in) over 10 years.[19][20]

    Hypersensitivity (including skin rash, urticaria, and fever) is sometimes reported when using transdermal methylphenidate. The Daytrana patch has a much higher rate of skin reactions than oral methylphenidate.[21]

    Methylphenidate can worsen psychosis in people who are psychotic, and in very rare cases it has been associated with the emergence of new psychotic symptoms.[22] It should be used with extreme caution in people with bipolar disorder due to the potential induction of mania or hypomania.[23] There have been very rare reports of suicidal ideation, but some authors claim that evidence does not support a link.[18] Logorrhea is occasionally reported. Libido disorders, disorientation, and hallucinations are very rarely reported. Priapism is a very rare adverse event that can be potentially serious.[24]

    USFDA-commissioned studies from 2011 indicate that in children, young adults, and adults there is no association between serious adverse cardiovascular events (sudden death, heart attack, and stroke) and the medical use of methylphenidate or other ADHD stimulants.[25]

    Because some adverse effects may only emerge during chronic use of methylphenidate, a constant watch for adverse effects is recommended.[26]

    A 2018 Cochrane review found that methylphenidate might be associated with serious side effects such as heart problems, psychosis, and death; the certainty of the evidence was stated as very low and the actual risk might be higher.[27]

    Overdose

    The symptoms of a moderate acute overdose on methylphenidate primarily arise from central nervous system overstimulation; these symptoms include: vomiting, nausea, agitation, tremors, hyperreflexia, muscle twitching, euphoria, confusion, hallucinations, delirium, hyperthermia, sweating, flushing, headache, tachycardia, heart palpitations, cardiac arrhythmias, hypertension, mydriasis, and dryness of mucous membranes.[28][29] A severe overdose may involve symptoms such as hyperpyrexia, sympathomimetic toxidrome, convulsions, paranoia, stereotypy (a repetitive movement disorder), rapid muscle breakdown, coma, and circulatory collapse.[28][29][30] A methylphenidate overdose is rarely fatal with appropriate care.[30] Following injection of methylphenidate tablets into an artery, severe toxic reactions involving abscess formation and necrosis have been reported.[31]

    Treatment of a methylphenidate overdose typically involves the administration of benzodiazepines, with antipsychotics, α-adrenoceptor agonists and propofol serving as second-line therapies.[30]

    Addiction and dependence
    ΔFosB accumulation from excessive drug use
    Top: this depicts the initial effects of high dose exposure to an addictive drug on gene expression in the nucleus accumbens for various Fos family proteins (i.e., c-Fos, FosB, ΔFosB, Fra1, and Fra2).
    Bottom: this illustrates the progressive increase in ΔFosB expression in the nucleus accumbens following repeated twice daily drug binges, where these phosphorylated (35–37 kilodalton) ΔFosB isoforms persist in the D1-type medium spiny neurons of the nucleus accumbens for up to 2 months.[32][33]

    Methylphenidate is a stimulant with an addiction liability and dependence liability similar to amphetamine. It has moderate liability among addictive drugs;[34][35] accordingly, addiction and psychological dependence are possible and likely when methylphenidate is used at high doses as a recreational drug.[35][36] When used above the medical dose range, stimulants are associated with the development of stimulant psychosis.[37] As with all addictive drugs, the overexpression of ΔFosB in D1-type medium spiny neurons in the nucleus accumbens is implicated in methylphenidate addiction.[36][38]

    Methylphenidate has shown some benefits as a replacement therapy for individuals who are addicted to and dependent upon methamphetamine.[39] Methylphenidate and amphetamine have been investigated as a chemical replacement for the treatment of cocaine addiction[40][41][42][43] in the same way that methadone is used as a replacement drug for physical dependence upon heroin. Its effectiveness in treatment of cocaine or psychostimulant addiction, or psychological dependence has not been proven and further research is needed.[44]

    Biomolecular mechanisms
    Further information: Addiction § Biomolecular mechanisms

    Methylphenidate has the potential to induce euphoria due to its pharmacodynamic effect (i.e., dopamine reuptake inhibition) in the brain's reward system.[38] At therapeutic doses, ADHD stimulants do not sufficiently activate the reward system, or the reward pathway in particular, to the extent necessary to cause persistent increases in ΔFosB gene expression in the D1-type medium spiny neurons of the nucleus accumbens;[35][38][45] consequently, when taken as directed in doses that are commonly prescribed for the treatment of ADHD, methylphenidate use lacks the capacity to cause an addiction.[35][38][45] However, when methylphenidate is used at sufficiently high recreational doses through a bioavailable route of administration (e.g., insufflation or intravenous administration), particularly for use of the drug as a euphoriant, ΔFosB accumulates in the nucleus accumbens.[35][38] Hence, like any other addictive drug, regular recreational use of methylphenidate at high doses eventually gives rise to ΔFosB overexpression in D1-type neurons which subsequently triggers a series of gene transcription-mediated signaling cascades that induce an addiction.[38][45][46]

    Overdose

    The symptoms of a moderate acute overdose on methylphenidate primarily arise from central nervous system overstimulation; these symptoms include: vomiting, nausea, agitation, tremors, hyperreflexia, muscle twitching, euphoria, confusion, hallucinations, delirium, hyperthermia, sweating, flushing, headache, tachycardia, heart palpitations, cardiac arrhythmias, hypertension, mydriasis, and dryness of mucous membranes.[28][29] A severe overdose may involve symptoms such as hyperpyrexia, sympathomimetic toxidrome, convulsions, paranoia, stereotypy (a repetitive movement disorder), rapid muscle breakdown, coma, and circulatory collapse.[28][29][30] A methylphenidate overdose is rarely fatal with appropriate care.[30] Following injection of methylphenidate tablets into an artery, severe toxic reactions involving abscess formation and necrosis have been reported.[31]

    Treatment of a methylphenidate overdose typically involves the administration of benzodiazepines, with antipsychotics, α-adrenoceptor agonists and propofol serving as second-line therapies.[30]

    Interactions

    Methylphenidate may inhibit the metabolism of vitamin K anticoagulants, certain anticonvulsants, and some antidepressants (tricyclic antidepressants, and selective serotonin reuptake inhibitors). Concomitant administration may require dose adjustments, possibly assisted by monitoring of plasma drug concentrations.[47] There are several case reports of methylphenidate inducing serotonin syndrome with concomitant administration of antidepressants.[48][49][50][51]

    When methylphenidate is coingested with ethanol, a metabolite called ethylphenidate is formed via hepatic transesterification,[52][53] not unlike the hepatic formation of cocaethylene from cocaine and ethanol. The reduced potency of ethylphenidate and its minor formation means it does not contribute to the pharmacological profile at therapeutic doses and even in overdose cases ethylphenidate concentrations remain negligible.[54][53]

    Coingestion of alcohol (ethanol) also increases the blood plasma levels of d-methylphenidate by up to 40%.[55]

    Liver toxicity from methylphenidate is extremely rare, but limited evidence suggests that intake of β-adrenergic agonists with methylphenidate may increase the risk of liver toxicity.[56]

    Mode of activity

    Methylphenidate is a catecholamine reuptake inhibitor that indirectly increases catecholaminergic neurotransmission by inhibiting the dopamine transporter (DAT) and norepinephrine transporter (NET),[57] which are responsible for clearing catecholamines from the synapse, particularly in the striatum and meso-limbic system.[58] Moreover, it is thought to "increase the release of these monoamines into the extraneuronal space."[59]

    Although four stereoisomers of methylphenidate (MPH) are possible, only the threo diastereoisomers are used in modern practice. There is a high eudysmic ratio between the SS and RR enantiomers of MPH. Dexmethylphenidate (d-threo-methylphenidate) is a preparation of the RR enantiomer of methylphenidate.[60][61] In theory, D-TMP (d-threo-methylphenidate) can be anticipated to be twice the strength of the racemic product.[57][62]

    Compd[63] DAT (Ki) DA (IC50) NET (Ki) NE (IC50)
    D-TMP1612320639
    L-TMP22501600>10K980
    DL-TMP1212078851

    Pharmacology
    Main article: Methylphenidate § Pharmacology

    Dexmethylphenidate has a 4–6 hour duration of effect (a long-acting formulation, Focalin XR, which spans 12 hours is also available and has been shown to be as effective as DL (dextro-, levo-)-TMP (threo-methylphenidate) XR (extended release) (Concerta, Ritalin LA), with flexible dosing and good tolerability.[64][65]) It has also been demonstrated to reduce ADHD symptoms in both children[66] and adults.[67] d-MPH has a similar side-effect profile to MPH[14] and can be administered without regard to food intake.[68]

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    35. Malenka RC, Nestler EJ, Hyman SE (2009). "Chapter 15: Reinforcement and Addictive Disorders". In Sydor A, Brown RY (eds.). Molecular Neuropharmacology: A Foundation for Clinical Neuroscience (2nd ed.). New York: McGraw-Hill Medical. p. 368. ISBN 9780071481274. Cocaine, [amphetamine], and methamphetamine are the major psychostimulants of abuse. The related drug methylphenidate is also abused, although it is far less potent. These drugs elicit similar initial subjective effects ; differences generally reflect the route of administration and other pharmacokinetic factors. Such agents also have important therapeutic uses; cocaine, for example, is used as a local anesthetic (Chapter 2), and amphetamines and methylphenidate are used in low doses to treat attention deficit hyperactivity disorder and in higher doses to treat narcolepsy (Chapter 12). Despite their clinical uses, these drugs are strongly reinforcing, and their long-term use at high doses is linked with potential addiction, especially when they are rapidly administered or when high-potency forms are given.
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    45. Nestler EJ (December 2013). "Cellular basis of memory for addiction". Dialogues in Clinical Neuroscience. 15 (4): 431–43. PMC 3898681. PMID 24459410. Despite the importance of numerous psychosocial factors, at its core, drug addiction involves a biological process: the ability of repeated exposure to a drug of abuse to induce changes in a vulnerable brain that drive the compulsive seeking and taking of drugs, and loss of control over drug use, that define a state of addiction. ... A large body of literature has demonstrated that such ΔFosB induction in D1-type NAc neurons increases an animal's sensitivity to drug as well as natural rewards and promotes drug self-administration, presumably through a process of positive reinforcement ... Another ΔFosB target is cFos: as ΔFosB accumulates with repeated drug exposure it represses c-Fos and contributes to the molecular switch whereby ΔFosB is selectively induced in the chronic drug-treated state.41. ... Moreover, there is increasing evidence that, despite a range of genetic risks for addiction across the population, exposure to sufficiently high doses of a drug for long periods of time can transform someone who has relatively lower genetic loading into an addict.4
    46. Ruffle JK (November 2014). "Molecular neurobiology of addiction: what's all the (Δ)FosB about?". The American Journal of Drug and Alcohol Abuse. 40 (6): 428–37. doi:10.3109/00952990.2014.933840. PMID 25083822.
      The strong correlation between chronic drug exposure and ΔFosB provides novel opportunities for targeted therapies in addiction (118), and suggests methods to analyze their efficacy (119). Over the past two decades, research has progressed from identifying ΔFosB induction to investigating its subsequent action (38). It is likely that ΔFosB research will now progress into a new era – the use of ΔFosB as a biomarker. ...
      Conclusions
           ΔFosB is an essential transcription factor implicated in the molecular and behavioral pathways of addiction following repeated drug exposure. The formation of ΔFosB in multiple brain regions, and the molecular pathway leading to the formation of AP-1 complexes is well understood. The establishment of a functional purpose for ΔFosB has allowed further determination as to some of the key aspects of its molecular cascades, involving effectors such as GluR2 (87,88), Cdk5 (93) and NFkB (100). Moreover, many of these molecular changes identified are now directly linked to the structural, physiological and behavioral changes observed following chronic drug exposure (60,95,97,102). New frontiers of research investigating the molecular roles of ΔFosB have been opened by epigenetic studies, and recent advances have illustrated the role of ΔFosB acting on DNA and histones, truly as a molecular switch (34). As a consequence of our improved understanding of ΔFosB in addiction, it is possible to evaluate the addictive potential of current medications (119), as well as use it as a biomarker for assessing the efficacy of therapeutic interventions (121,122,124). Some of these proposed interventions have limitations (125) or are in their infancy (75). However, it is hoped that some of these preliminary findings may lead to innovative treatments, which are much needed in addiction.
      • Biliński P, Wojtyła A, Kapka-Skrzypczak L, Chwedorowicz R, Cyranka M, Studziński T (2012). "Epigenetic regulation in drug addiction". Annals of Agricultural and Environmental Medicine. 19 (3): 491–6. PMID 23020045. For these reasons, ΔFosB is considered a primary and causative transcription factor in creating new neural connections in the reward centre, prefrontal cortex, and other regions of the limbic system. This is reflected in the increased, stable and long-lasting level of sensitivity to cocaine and other drugs, and tendency to relapse even after long periods of abstinence. These newly constructed networks function very efficiently via new pathways as soon as drugs of abuse are further taken ... In this way, the induction of CDK5 gene expression occurs together with suppression of the G9A gene coding for dimethyltransferase acting on the histone H3. A feedback mechanism can be observed in the regulation of these 2 crucial factors that determine the adaptive epigenetic response to cocaine. This depends on ΔFosB inhibiting G9a gene expression, i.e. H3K9me2 synthesis which in turn inhibits transcription factors for ΔFosB. For this reason, the observed hyper-expression of G9a, which ensures high levels of the dimethylated form of histone H3, eliminates the neuronal structural and plasticity effects caused by cocaine by means of this feedback which blocks ΔFosB transcription
      • Robison AJ, Nestler EJ (October 2011). "Transcriptional and epigenetic mechanisms of addiction". Nature Reviews. Neuroscience. 12 (11): 623–37. doi:10.1038/nrn3111. PMC 3272277. PMID 21989194. ΔFosB has been linked directly to several addiction-related behaviors ... Importantly, genetic or viral overexpression of ΔJunD, a dominant negative mutant of JunD which antagonizes ΔFosB- and other AP-1-mediated transcriptional activity, in the NAc or OFC blocks these key effects of drug exposure14,22–24. This indicates that ΔFosB is both necessary and sufficient for many of the changes wrought in the brain by chronic drug exposure. ΔFosB is also induced in D1-type NAc MSNs by chronic consumption of several natural rewards, including sucrose, high fat food, sex, wheel running, where it promotes that consumption14,26–30. This implicates ΔFosB in the regulation of natural rewards under normal conditions and perhaps during pathological addictive-like states.
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