Atomoxetine, sold under the brand name Strattera, is a medication used to treat attention deficit hyperactivity disorder (ADHD) [12] and, to a lesser extent, cognitive disengagement syndrome. [13] [14] [15] It may be used alone or along with psychostimulants. [16] [17] It is also used as a cognitive and executive functioning enhancer to improve self-motivation, persistence, attention, inhibition, and working memory. [18] [19] [20] Use of atomoxetine is only recommended for those who are at least six years old. [12] It is taken orally. [12] Atomoxetine is a selective norepinephrine reuptake inhibitor and is believed to work by increasing norepinephrine and dopamine levels in the brain. [12] [10] The effectiveness of atomoxetine is comparable to the commonly prescribed stimulant medication methylphenidate. [21] [22] [23] [24]
Common side effects of atomoxetine include abdominal pain, loss of appetite, nausea, feeling tired, and dizziness. [12] Serious side effects may include angioedema, liver problems, stroke, psychosis, heart problems, suicide, and aggression. [12] [25] There is a lack of data regarding its safety during pregnancy; as of 2019, its safety during pregnancy and for use during breastfeeding is not certain. [26] [27]
It was approved for medical use in the United States in 2002. [12] In 2021, it was the 219th most commonly prescribed medication in the United States, with more than 1.9 million prescriptions. [28] [29]
Atomoxetine is indicated for the treatment of attention deficit hyperactivity disorder (ADHD). [5]
Atomoxetine is approved for use in children, adolescents, and adults. [5] However, its efficacy has not been studied in children under six years old. [8] One of the primary differences with the standard stimulant treatments for ADHD is that it has little known abuse potential. [8] Meta-analyses and systematic reviews have found that atomoxetine has comparable efficacy and equal tolerability to methylphenidate in children and adolescents. In adults, efficacy and tolerability are equivalent. [21] [22] [23] [24]
While its efficacy may be less than that of amphetamine, [30] there is some evidence that it may be used in combination with stimulants. [16] Doctors may prescribe non-stimulants including atomoxetine when a person has bothersome side effects from stimulants; when a stimulant was not effective; in combination with a stimulant to increase effectiveness; [31] [32] when the cost of stimulants is prohibitive; or when there is concern about the abuse potential of psychostimulants in a patient with a history of drug use disorder.
Unlike α2 adrenoceptor agonists such as guanfacine and clonidine, atomoxetine's use can be abruptly stopped without significant discontinuation effects being seen. [8]
The initial therapeutic effects of atomoxetine usually take 1 to 4 weeks to become apparent. [7] [33] [34] A further 2 to 4 weeks may be required for the full therapeutic effects to be seen. [35] [33] Incrementally increasing response may occur up to 1 year or longer. [34] [36] The maximum recommended total daily dose in children and adolescents over 70 kg and adults is 100 mg. [5]
Atomoxetine may be used to treat cognitive disengagement syndrome (CDS), [37] as multiple controlled clinical trials have found that it is an effective treatment. [38] [39] [40] In contrast, CDS is associated with poor or insignificant treatment response to the stimulant medication methylphenidate. [41] [42] [43] [44]
Atomoxetine is sometimes used in the treatment of cognitive impairment and frontal lobe symptoms due to conditions like traumatic brain injury (TBI). [45] [46] It is used with the goal of treating ADHD-like symptoms such as sustained attentional problems, disinhibition, [47] lack of arousal, fatigue, and depression, including symptoms from cognitive disengagement syndrome. [45] A 2015 Cochrane review identified only one study of atomoxetine for TBI and found no positive effects. [48] Aside from TBI, atomoxetine was found to be effective in the treatment of akinetic mutism following subarachnoid hemorrhage in a case report. [46] [49]
Contraindications include: [8]
Common side effects include abdominal pain, loss of appetite, nausea, feeling tired, and dizziness. [12] Serious side effects may include angioedema, liver problems, stroke, psychosis, heart problems, suicide, and aggression. [12] [25] A 2020 meta-analysis found that atomoxetine was associated with anorexia, weight loss, and hypertension, rating it as a "potentially least preferred agent based on safety" for treating ADHD. [50] [51] As of 2019, safety in pregnancy and breastfeeding is not clear; [26] a 2018 review stated that, "[b]ecause of lack of data, the treating physician should consider stopping atomoxetine treatment in women with ADHD during pregnancy." [27]
The U.S. Food and Drug Administration (FDA) has issued a black box warning for suicidal behavior/ideation. [9] Similar warnings have been issued in Australia. [8] [52] Unlike stimulant medications, atomoxetine does not have abuse liability or the potential to cause withdrawal effects on abrupt discontinuation. [8] [53]
Atomoxetine is relatively non-toxic in overdose. Single-drug overdoses involving over 1500 mg of atomoxetine have not resulted in death. [8]
Atomoxetine is a substrate for CYP2D6. Concurrent treatment with a CYP2D6 inhibitor such as bupropion, fluoxetine, or paroxetine has been shown to increase plasma atomoxetine by 100% or more, as well as increase N-desmethylatomoxetine levels and decrease plasma 4-hydroxyatomoxetine levels by a similar degree. [54] [55] [56]
Atomoxetine has been found to directly inhibit hERG potassium currents with an IC50 of 6.3 μM, which has the potential to cause arrhythmia. [55] [57] QT prolongation has been reported with atomoxetine at therapeutic doses and in overdose; it is suggested that atomoxetine not be used with other medications that may prolong the QT interval, concomitantly with CYP2D6 inhibitors, and caution to be used in poor metabolizers. [55]
Other notable drug interactions include: [8]
Site | ATX | 4-OH-ATX | N-DM-ATX | |
---|---|---|---|---|
SERT | 77 | 43 | ND | |
NET | 5 | 3 | 92 | |
DAT | 1,451 | ND | ND | |
5-HT1A | >1,000 | ND | ND | |
5-HT1B | >1,000 | ND | ND | |
5-HT1D | >1,000 | ND | ND | |
5-HT2 | 2,000 | 1,000 | 1,700 | |
5-HT6 | >1,000 | ND | ND | |
5-HT7 | >1,000 | ND | ND | |
α1 | 11,400 | 20,000 | 19,600 | |
α2A | 29,800 | >30,000 | >10,000 | |
β1 | 18,000 | 56,100 | 32,100 | |
M1 | >100,000 | >100,000 | >100,000 | |
M2 | >100,000 | >100,000 | >100,000 | |
D1 | >10,000 | >10,000 | >10,000 | |
D2 | >10,000 | >10,000 | >10,000 | |
H1 | 12,100 | >100,000 | >100,000 | |
MOR | Antagonist | 422 | ND | |
DOR | ND | 300 | ND | |
KOR | Partial Agonist | 95 | ND | |
σ1 | >1,000 | ND | ND | |
GABAA | 200 | >30,000 | >10,000 | |
NMDA | 0.66 - 3,470a | ND | ND | |
Kir3.1/3.2 | 10,900b | ND | ND | |
Kir3.2 | 12,400b | ND | ND | |
Kir3.1/3.4 | 6,500b | ND | ND | |
hERG | 6,300 | 20,000 | 5,710 | |
Values are Ki (nM). The smaller the value, the more strongly the drug binds to the site. All values are for human receptors unless otherwise specified. arat cortex. bXenopus oocytes. Additional sources: [61] [62] [10] [58] |
Atomoxetine inhibits the presynaptic norepinephrine transporter (NET), preventing the reuptake of norepinephrine throughout the brain along with inhibiting the reuptake of dopamine in specific brain regions such as the prefrontal cortex, where dopamine transporter (DAT) expression is minimal. [10] In rats, atomoxetine increased prefrontal cortex catecholamine concentrations without altering dopamine levels in the striatum or nucleus accumbens; in contrast, methylphenidate, a dopamine reuptake inhibitor, was found to increase prefrontal, striatal, and accumbal dopamine levels to the same degree. [61] In addition to rats, atomoxetine has also been found to induce similar region-specific catecholamine level alteration in mice. [63]
Atomoxetine's status as a serotonin transporter (SERT) inhibitor at clinical doses in humans is uncertain. A PET imaging study on rhesus monkeys found that atomoxetine occupied >90% and >85% of neural NET and SERT, respectively. [64] However, both mouse and rat microdialysis studies have failed to find an increase in extracellular serotonin in the prefrontal cortex following acute or chronic atomoxetine treatment. [61] [63] Supporting atomoxetine's selectivity, a human study found no effects on platelet serotonin uptake (a marker of SERT inhibition) and inhibition of the pressor effects of tyramine (a marker of NET inhibition). [65]
Atomoxetine has been found to act as an NMDA receptor antagonist in rat cortical neurons at therapeutic concentrations. [66] [67] It causes a use-dependent open-channel block and its binding site overlaps with the Mg2+ binding site. [66] [67] Atomoxetine's ability to increase prefrontal cortex firing rate in anesthetized rats could not be blocked by D1 or α1-adrenergic receptor antagonists, but could be potentiated by NMDA or an α2-adrenergic receptor antagonist, suggesting a glutaminergic mechanism. [68] In Sprague Dawley rats, atomoxetine reduces NR2B protein content without altering transcript levels. [69] Aberrant glutamate and NMDA receptor function have been implicated in the etiology of ADHD. [70] [71]
Atomoxetine also reversibly inhibits GIRK currents in Xenopus oocytes in a concentration-dependent, voltage-independent, and time-independent manner. [72] Kir3.1/3.2 ion channels are opened downstream of M2, α2, D2, and A1 stimulation, as well as other Gi-coupled receptors. [72] Therapeutic concentrations of atomoxetine are within range of interacting with GIRKs, especially in CYP2D6 poor metabolizers. [72] It is not known whether this contributes to the therapeutic effects of atomoxetine in ADHD.
4-Hydroxyatomoxetine, the major active metabolite of atomoxetine in CYP2D6 extensive metabolizers, has been found to have sub-micromolar affinity for opioid receptors, acting as an antagonist at μ-opioid receptors and a partial agonist at κ-opioid receptors. [62] It is not known whether this action at the kappa-opioid receptor leads to CNS-related adverse effects.
Orally administered atomoxetine is rapidly and completely absorbed. [10] First-pass metabolism by the liver is dependent on CYP2D6 activity, resulting in an absolute bioavailability of 63% for extensive metabolizers and 94% for poor metabolizers. [10] Maximum plasma concentration is reached in 1–2 hours. [10] If taken with food, the maximum plasma concentration decreases by 10-40% and delays the tmax by 3 hours. [10] Drugs affecting gastric pH have no effect on oral bioavailability. [5]
Following intravenous delivery, atomoxetine has a volume of distribution of 0.85 L/kg (indicating distribution primarily in total body water), with limited partitioning into red blood cells. [10] [73] It is highly bound to plasma proteins (98.7%), mainly albumin, along with α1-acid glycoprotein (77%) and IgG (15%). [10] [58] Its metabolite N-desmethylatomoxetine is 99.1% bound to plasma proteins, while 4-hydroxyatomoxetine is only 66.6% bound. [10]
The half-life of atomoxetine varies widely between individuals, with an average range of 4.5 to 19 hours. [10] [11] As atomoxetine is metabolized by CYP2D6, exposure may be increased 10-fold in CYP2D6 poor metabolizers. [11] Among CYP2D6 extensive metabolizers, the half-life of atomoxetine averaged 5.34 hours and the half-life of the active metabolite N-desmethylatomoxetine was 8.9 hours. [10] [74] By contrast, among CYP2D6 poor metabolizers the half-life of atomoxetine averaged 20.0 hours and the half-life of N-desmethylatomoxetine averaged 33.3 hours. [10] [74] Steady-state levels of atomoxetine are typically achieved at or around day 10 of regular dosing, with trough plasma concentrations (Ctrough) residing around 30–40°ng/mL; however, both the time to steady-state levels and Ctrough are expected to vary based on a patient's CYP2D6 profile. [75] [76]
Atomoxetine, N-desmethylatomoxetine, and 4-hydroxyatomoxetine produce minimal to no inhibition of CYP1A2 and CYP2C9, but inhibit CYP2D6 in human liver microsomes at concentrations between 3.6 and 17 μmol/L.[ citation needed ] Plasma concentrations of 4-hydroxyatomoxetine and N-desmethylatomoxetine at steady state are 1.0% and 5% that of atomoxetine in CYP2D6 extensive metabolizers, and are 5% and 45% that of atomoxetine in CYP2D6 poor metabolizers. [5]
Atomoxetine is excreted unchanged in urine at <3% in both extensive and poor CYP2D6 metabolizers, with >96% and 80% of a total dose being excreted in urine, respectively. [10] The fractions excreted in urine as 4-hydroxyatomoxetine and its glucuronide account for 86% of a given dose in extensive metabolizers, but only 40% in poor metabolizers. [10] CYP2D6 poor metabolizers excrete greater amounts of minor metabolites, namely N-desmethylatomoxetine and 2-hydroxymethylatomoxetine and their conjugates. [10]
Chinese adults homozygous for the hypoactive CYP2D6*10 allele have been found to exhibit two-fold higher area-under-the-curve (AUCs) and 1.5-fold higher maximum plasma concentrations compared to extensive metabolizers. [10]
Japanese men homozygous for CYP2D6*10 have similarly been found to experience two-fold higher AUCs compared to extensive metabolizers. [10]
Atomoxetine, or (−)-methyl[(3R)-3-(2-methylphenoxy)-3-phenylpropylamine, is a white, granular powder that is highly soluble in water.
Atomoxetine may be quantitated in plasma, serum or whole blood in order to distinguish extensive versus poor metabolizers in those receiving the drug therapeutically, to confirm the diagnosis in potential poisoning victims or to assist in the forensic investigation in a case of fatal overdosage. [79]
Atomoxetine is manufactured, marketed, and sold in the United States as the hydrochloride salt (atomoxetine HCl) under the brand name Strattera by Eli Lilly and Company, the original patent-filing company and current U.S. patent owner. Atomoxetine was initially intended to be developed as an antidepressant, but it was found to be insufficiently efficacious for treating depression. It was, however, found to be effective for ADHD and was approved by the FDA in 2002, for the treatment of ADHD. Its patent expired in May 2017. [80] On 12 August 2010, Lilly lost a lawsuit that challenged its patent on Strattera, increasing the likelihood of an earlier entry of a generic into the US market. [81] On 1 September 2010, Sun Pharmaceuticals announced it would begin manufacturing a generic in the United States. [82] In a 29 July 2011 conference call, however, Sun Pharmaceutical's Chairman stated "Lilly won that litigation on appeal so I think [generic Strattera]'s deferred." [83]
In 2017 the FDA approved the generic production of atomoxetine by four pharmaceutical companies. [84]
The drug was originally known as tomoxetine. It was renamed to avoid medication errors, as the name may be confused with tamoxifen. [85]
In India, atomoxetine is sold under brand names including Axetra, Axepta, Attera, Tomoxetin, and Attentin. In Australia, Canada, Italy, Portugal, Romania, Spain, Switzerland and the US, atomoxetine is sold under the brand name Strattera. In the Czech Republic it is sold under brand names including Mylan. In Poland, it is sold under the brand name Auroxetyn. In Iran, atomoxetine is sold under brand names including Stramox. In 2017, a generic version was approved in the United States. [84]
There has been some suggestion that atomoxetine might be a helpful adjunct in people with major depression, particularly in cases with concomitant ADHD. [86]
Atomoxetine may be used in those with ADHD and bipolar disorder although such use has not been well studied. [87] Some benefit has also been seen in people with ADHD and autism. [88] As with other norepinephrine reuptake inhibitors it appears to reduce anxiety and depression symptoms, although attention has focused mainly on specific patient groups such as those with concurrent ADHD [89] or methamphetamine dependence. [90]
Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder characterised by executive dysfunction occasioning symptoms of inattention, hyperactivity, impulsivity and emotional dysregulation that are excessive and pervasive, impairing in multiple contexts, and otherwise age-inappropriate.
Methylphenidate, sold under the brand names Ritalin and Concerta among others, is a potent 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. For ADHD, the effectiveness of methylphenidate is comparable to atomoxetine but modestly lower than amphetamines.
Dextroamphetamine (INN:dexamfetamine) is a potent central nervous system (CNS) stimulant and enantiomer of amphetamine that is prescribed for the treatment of attention deficit hyperactivity disorder (ADHD) and narcolepsy. It is also used as an athletic performance and cognitive enhancer, and recreationally as an aphrodisiac and euphoriant.
Clonidine, sold under the brand name Catapres among others, is an α2a-adrenergic agonist medication used to treat high blood pressure, ADHD, drug withdrawal, menopausal flushing, diarrhea, spasticity, and certain pain conditions. The drug is often prescribed off-label for tics. It is used orally, by injection, or as a transdermal skin patch. Onset of action is typically within an hour with the effects on blood pressure lasting for up to eight hours.
Adderall and Mydayis are trade names for a combination drug called mixed amphetamine salts containing four salts of amphetamine. The mixture is composed of equal parts racemic amphetamine and dextroamphetamine, which produces a (3:1) ratio between dextroamphetamine and levoamphetamine, the two enantiomers of amphetamine. Both enantiomers are stimulants, but differ enough to give Adderall an effects profile distinct from those of racemic amphetamine or dextroamphetamine, which are marketed as Evekeo and Dexedrine/Zenzedi, respectively. Adderall is used in the treatment of attention deficit hyperactivity disorder (ADHD) and narcolepsy. It is also used illicitly as an athletic performance enhancer, cognitive enhancer, appetite suppressant, and recreationally as a euphoriant. It is a central nervous system (CNS) stimulant of the phenethylamine class.
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.
Reboxetine, sold under the brand name Edronax among others, is a drug of the norepinephrine reuptake inhibitor (NRI) class, marketed as an antidepressant by Pfizer for use in the treatment of major depression, although it has also been used off-label for panic disorder and attention deficit hyperactivity disorder (ADHD). It is approved for use in many countries worldwide, but has not been approved for use in the United States. Although its effectiveness as an antidepressant has been challenged in multiple published reports, its popularity has continued to increase.
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.
Adult Attention Deficit Hyperactivity Disorder is the persistence of attention deficit hyperactivity disorder (ADHD) in adults. It is a neurodevelopmental disorder, meaning symptoms must have been present in childhood except for when ADHD occurs after a traumatic brain injury. Specifically, multiple symptoms must be present before the age of 12, according to DSM-5 diagnostic criteria. The cutoff age of 12 is a change from the previous requirement of symptom onset, which was before the age of 7 in the DSM-IV. This was done to add flexibility in the diagnosis of adults. ADHD was previously thought to be a childhood disorder that improved with age, but recent research has disproved this. Approximately two-thirds of childhood cases of ADHD continue into adulthood, with varying degrees of symptom severity that change over time, and continue to affect individuals with symptoms ranging from minor inconveniences to impairments in daily functioning.
Viloxazine, sold under the brand name Qelbree and formerly as Vivalan among others, is a selective norepinephrine reuptake inhibitor medication which is used in the treatment of attention deficit hyperactivity disorder (ADHD) in children and adults. It was marketed for almost 30 years as an antidepressant for the treatment of depression before being discontinued and subsequently repurposed as a treatment for ADHD. Viloxazine is taken orally. It was used as an antidepressant in an immediate-release form and is used in ADHD in an extended-release form.
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.
Guanfacine, sold under the brand name Tenex (immediate-release) and Intuniv (extended-release) among others, is an oral alpha-2a agonist medication used to treat attention deficit hyperactivity disorder (ADHD) and high blood pressure. Guanfacine is FDA-approved for monotherapy treatment of ADHD, as well as being used for augmentation of other treatments, such as stimulants. Guanfacine is also used off-label to treat tic disorders, anxiety disorders, and post-traumatic stress disorder (PTSD).
Attention deficit hyperactivity disorder predominantly inattentive, is one of the three presentations of attention deficit hyperactivity disorder (ADHD). In 1987–1994, there were no subtypes and thus it was not distinguished from hyperactive ADHD in the Diagnostic and Statistical Manual (DSM-III-R).
Despite the scientifically well-established nature of attention deficit hyperactivity disorder (ADHD), its diagnosis, and its treatment, each of these has been controversial since the 1970s. The controversies involve clinicians, teachers, policymakers, parents, and the media. Positions range from the view that ADHD is within the normal range of behavior to the hypothesis that ADHD is a genetic condition. Other areas of controversy include the use of stimulant medications in children, the method of diagnosis, and the possibility of overdiagnosis. In 2009, the National Institute for Health and Care Excellence, while acknowledging the controversy, stated that the current treatments and methods of diagnosis are based on the dominant view of the academic literature.
Lisdexamfetamine, sold under the brand names Vyvanse and Elvanse among others, is a stimulant medication that is used to treat attention deficit hyperactivity disorder (ADHD) in children and adults and for moderate-to-severe binge eating disorder in adults. Lisdexamfetamine is taken by mouth. Its effects generally begin within two hours and last for up to 14 hours. In the United Kingdom, it is usually less preferred to methylphenidate for the treatment of children.
Attention deficit hyperactivity disorder management options are evidence-based practices with established treatment efficacy for ADHD.
Selective norepinephrine reuptake inhibitors (sNRIs) are a class of drugs that have been marketed as antidepressants and are used for various mental disorders, mainly depression and attention-deficit hyperactivity disorder (ADHD). The norepinephrine transporter (NET) serves as the fundamental mechanism for the inactivation of noradrenergic signaling because of the NET termination in the reuptake of norepinephrine (NE). The selectivity and mechanism of action for the NRI drugs remain mostly unresolved and, to date, only a limited number of NRI-selective inhibitors are available. The first commercially available selective NRI was the drug reboxetine (Edronax), developed as a first-line therapy for major depressive disorder. Atomoxetine (Strattera) is another potent and selective NRI which is also effective and well tolerated for the treatment of ADHD in adults; it may also be a new treatment option for adults with ADHD, particularly for those patients at risk of substance abuse.
Though not FDA-approved for combined treatment, atomoxetine (Strattera) is sometimes used in conjunction with stimulants as an off-label combination therapy.
Atomoxetine is a nonstimulant drug used to treat ADHD (Perwien et al., 2006) that acts as a presynaptic blocker of noradrenalin reuptake (Swanson et al., 2006).
The noradrenergic action also exerts an important clinical effect in different antidepressant classes such as desipramine and nortriptyline (tricyclics, prevalent noradrenergic effect), reboxetine and atomoxetine (relatively pure noradrenergic reuptake inhibitor (NRIs)), and dual action antidepressants such as the serotonin noradrenaline reuptake inhibitors (SNRIs), the noradrenergic and dopaminergic reuptake inhibitor (NDRI) bupropion, and other compounds (e.g., mianserin, mirtazapine), which enhance the noradrenergic transmission
Atomoxetine (Strattera) has also been researched in controlled studies for treatment of ADHD in children with autism, and showed some improvements, particularly for hyperactivity and impulsivity