ADHD

Attention-Deficit/Hyperactivity Disorder (ADHD) is a neurodevelopmental disorder characterised by a persistent pattern of inattention and/or hyperactivity-impulsivity that is developmentally inappropriate, present before age 12, observed across multiple settings, and causing significant functional impairment. It is one of the most prevalent psychiatric conditions in childhood, often persisting into adolescence and adulthood. References: DSM-5-TR, StatPearls (NCBI Bookshelf).

Attention-Deficit/Hyperactivity Disorder (ADHD) is a neurodevelopmental disorder characterised by a persistent pattern of inattention and/or hyperactivity-impulsivity that is developmentally inappropriate, present before age 12, observed across multiple settings, and causing significant functional impairment. It is one of the most prevalent psychiatric conditions in childhood, often persisting into adolescence and adulthood. DSM-5-TR classifies ADHD under Neurodevelopmental Disorders with three presentations: predominantly inattentive, predominantly hyperactive-impulsive, and combined. ADHD reflects fundamental differences in brain development, particularly within prefrontal corticostriatal circuits governing executive function, working memory, inhibitory control, and emotional regulation. It is not caused by poor parenting, laziness, or lack of intelligence. This information is for psychoeducation only.

Inattentive symptoms (>=6 in children, >=5 in adults for >=6 months): failing to attend to details/careless mistakes; difficulty sustaining attention; not seeming to listen when spoken to directly; not following through on tasks; difficulty organising; avoiding sustained mental effort; frequently losing items; easily distracted by extraneous stimuli; forgetfulness in daily activities. Hyperactive-impulsive symptoms (>=6/5): fidgeting or squirming; leaving seat when expected to sit; running or climbing inappropriately (or inner restlessness in adults); unable to play quietly; 'on the go'/driven by a motor; talking excessively; blurting answers before questions are finished; difficulty waiting turn; interrupting/intruding. Additional features: emotional dysregulation, low frustration tolerance, mood lability, impulsive anger, time-blindness, and hyperfocus (intense attention on preferred activities) are frequently reported though not DSM-5 criteria.

Genetic: heritability ~70-80%; family history of ADHD increases risk 2-8 fold; candidate genes include DAT1, DRD4, DRD5; multiple common variants of small effect (polygenic). Prenatal: maternal smoking (one of the most replicated risk factors), alcohol/substance use in utero, prematurity, low birth weight, prenatal stress. Environmental: early childhood lead exposure; severe psychosocial adversity and neglect; traumatic brain injury to frontal regions.

Sex: diagnosed ~2:1 male to female in childhood (hyperactive presentation); ratio approaches 1:1 in adulthood; females more often present with inattentive subtype and are frequently underdiagnosed.

ADHD has a multifactorial aetiology. Neurobiologically, dysfunction in dopaminergic and noradrenergic pathways in the prefrontal cortex impairs executive function. The anterior cingulate cortex, caudate nucleus, and cerebellum show structural and functional differences. Neuroimaging shows delayed cortical maturation (3-5 years) in ADHD, especially in prefrontal regions, and hypoactivation of right frontostriatal circuits during inhibition tasks. No single gene causes ADHD; instead, additive effects of many common variants interact with environmental risk factors (gene-environment interaction). Prenatal neurotoxin exposure and epigenetic mechanisms also contribute. The dual-pathway model encompasses both a 'cool' executive/cognitive pathway and a 'hot' motivational/emotional pathway, both impaired in ADHD.

Global childhood prevalence: ~5-7%; adult prevalence ~2.5-4%. In the USA, ~9-10% of children aged 3-17 years have ever received an ADHD diagnosis (CDC). ADHD is diagnosed across all cultures; rate variation between countries reflects diagnostic practice differences. Male:female ratio ~2-3:1 in childhood, approaching 1:1 in adulthood. Approximately 50-65% of childhood cases persist into adulthood. Comorbidity is the rule: ~70% of individuals with ADHD have at least one other disorder, including ODD (~50%), conduct disorder (~25%), anxiety (~30-40%), depression (~20-30%), learning disabilities, tic disorders, and substance use disorders.

Catecholamine dysregulation is central: reduced dopamine (DA) and norepinephrine (NE) availability in the prefrontal cortex (PFC) impairs working memory, inhibitory control, and sustained attention. Stimulants block DA/NE reuptake transporters; amphetamines also stimulate release, restoring optimal catecholamine tone in PFC. Structural MRI: reduced total brain volume (~3-5%), greatest in caudate, cerebellar vermis, and prefrontal regions; these differences partially normalise in adulthood. Functional MRI: hypoactivation of right inferior frontal cortex and striatum during inhibition tasks; default mode network (DMN) fails to suppress during cognitive tasks, contributing to mind-wandering. White matter integrity (DTI) shows microstructural abnormalities in fronto-striatal tracts. BDNF signalling is implicated in neuroplasticity aspects.

Stimulant medication works by boosting dopamine and norepinephrine, allowing the prefrontal cortex to function more effectively. ADHD is not laziness or lack of intelligence; it is a neurodevelopmental difference that responds well to treatment. Diagnosis is clinical and requires: (1) Detailed history of symptoms across settings, onset before age 12, minimum 6-month duration, and functional impairment from patient and informants (parents, teachers, partners). (2) Rating scales: Conners scales, ADHD-RS-5, Vanderbilt (children); ASRS, CAARS, Brown ADD scales (adults). (3) Physical exam to exclude medical mimics: thyroid dysfunction, anaemia, vision/hearing problems, sleep disorders. (4) Cognitive/neuropsychological testing when learning disability or intellectual disability is suspected. (5) Collateral information: school records, teacher reports, work performance records.

DSM-5-TR criteria: Criterion A - persistent pattern of inattention (>=6 symptoms in children or >=5 in adults age >=17) and/or hyperactivity-impulsivity (>=6/5 symptoms), present for >=6 months to a degree inconsistent with developmental level. Criterion B - several symptoms present before age 12. Criterion C - symptoms present in >=2 settings. Criterion D - clear evidence of interference with functioning. Criterion E - not occurring exclusively during psychosis or better explained by another disorder. Specifiers: Combined presentation; Predominantly inattentive; Predominantly hyperactive-impulsive. Severity: Mild (few symptoms beyond threshold), Moderate, Severe (many excess symptoms/marked impairment). In partial remission: full criteria no longer met but impairment persists. ICD-11: code 6A05, similar structure; historically ICD-10 required symptoms across all settings (stricter).

Structured interviews: DIVA (Diagnostic Interview for ADHD in Adults), K-SADS (children), CAADID. Continuous Performance Tests (CPT): TOVA, Conners CPT - provide objective attention/impulsivity data (not diagnostic alone). Neuropsychological testing: useful when co-occurring learning disabilities or intellectual disability are suspected. Laboratory workup: thyroid function, CBC, lead level in young children, iron studies; no specific biomarker confirms ADHD. Bipolar screening (MDQ) before prescribing stimulants in adults. Comprehensive assessment should screen for all common comorbidities (anxiety, depression, ASD, substance use, learning disorders).

Anxiety disorders: worry-driven inattention, hyperarousal mimicking hyperactivity; unlike ADHD, anxiety is situational and driven by worry content. Depressive disorders: poor concentration, agitation, fatigue; onset typically later than ADHD. Bipolar disorder: elevated energy, distractibility, impulsivity are episodic and accompanied by mood elevation. Autism spectrum disorder (ASD): social communication deficits and restricted interests impair attention; ADHD and ASD can be co-diagnosed. Learning disorders: academic failure may be misattributed to ADHD without specific cognitive testing. Sleep disorders (OSA): sleep deprivation in children produces inattention/hyperactivity virtually identical to ADHD. Substance use: stimulant intoxication or withdrawal can mimic ADHD. PTSD: hypervigilance, concentration problems, and impulsivity following trauma may be misidentified.

Treatment of Attention-Deficit/Hyperactivity Disorder (ADHD) involves a multimodal approach combining psychoeducation, behavioural interventions, and pharmacotherapy. Treatment is tailored to the patient's age, symptom severity, functional impairment, and comorbid conditions. Psychoeducation: Educating the patient and family about ADHD as a neurodevelopmental condition is the foundation of treatment. Understanding that ADHD is not a character flaw but a brain-based condition with effective treatments reduces stigma and improves treatment adherence. Behavioural Interventions: For children, parent training in behaviour management is a first-line intervention. This includes structured routines, clear rules and expectations, positive reinforcement for desired behaviours, and consistent consequences. School-based accommodations (preferential seating, extended time, organisational support) are important. For adults, cognitive-behavioural therapy (CBT) adapted for ADHD targets executive function deficits, time management, organisational skills, and emotional regulation. Pharmacotherapy: Stimulant medications (methylphenidate and amphetamine-based preparations) are the first-line pharmacological treatment and are effective in approximately 70-80% of patients. They improve attention, reduce hyperactivity and impulsivity, and enhance academic and occupational functioning. Common formulations include immediate-release and extended-release preparations. Non-stimulant medications (atomoxetine, guanfacine extended-release, clonidine extended-release) are alternatives for patients who do not respond to or cannot tolerate stimulants, or who have comorbid conditions such as tic disorders or substance use risk. Bupropion and tricyclic antidepressants may be considered in select cases. Monitoring: Regular follow-up is essential to monitor treatment response, side effects (appetite suppression, sleep disturbance, cardiovascular effects), growth parameters in children, and the emergence of comorbid conditions. Dose adjustments are common as needs change across development. Lifestyle and Complementary Approaches: Regular physical exercise, adequate sleep, structured daily routines, and dietary balance support overall functioning. Mindfulness-based interventions may help with attention and emotional regulation. Coaching and organisational tools can be valuable adjuncts, especially for adults.

With treatment, most individuals achieve significant symptom reduction and functional improvement. ~70-80% respond to first stimulant tried. When non-response occurs, switching within or between stimulant classes is effective in many cases. ADHD is chronic in approximately 50-65% of childhood cases persisting to adulthood, often with shifts in presentation (reduced overt hyperactivity; persistent inattention and executive dysfunction). Longitudinal studies show early and sustained treatment improves academic achievement, social functioning, and reduces risk of substance use and accidents. Residual executive function deficits may persist even with good symptomatic response. Untreated ADHD is associated with higher rates of accidents, lower educational attainment, relationship instability, and premature mortality.

Academic and occupational underachievement: despite normal or above-average intelligence, individuals with untreated ADHD often underperform relative to potential—grades drop, projects go unfinished, and careers suffer from chronic lateness, disorganisation, and impulsivity. School dropout and job loss rates are elevated. Accident and injury risk: adults with ADHD have 2–4 times the rate of motor vehicle accidents; children have higher rates of unintentional injury. Substance use disorder risk is approximately doubled in untreated ADHD; stimulant treatment is protective, not a risk factor. Depression and anxiety commonly co-occur and worsen functional impairment. Conduct disorder and oppositional defiant disorder in childhood increase risk of antisocial personality disorder and criminal justice involvement in adulthood. Relationship instability: higher rates of marital difficulties, divorce, and parenting problems due to forgetfulness, emotional dysregulation, and conflict. Reduced life expectancy in severely affected untreated cases, driven by accidents, suicide, and comorbid conditions.

No proven primary prevention. Risk reduction: avoidance of smoking, alcohol, and drugs during pregnancy; adequate prenatal care; reducing early childhood lead exposure. Patient/family education: ADHD is a brain-based, genetic, chronic condition - not caused by poor parenting; symptoms are not wilful; medication is safe and evidence-based; structure, routines, and positive reinforcement are highly effective; comorbidities are common and should be assessed. For adults: psychoeducation about chronic nature, compensatory strategies (calendars, timers, task lists), and avoiding high-risk impulsive decisions. Early diagnosis and intervention dramatically improves long-term outcomes.

1902: Sir George Still described children with defects in 'moral control' and sustained attention. 1930s: labelled 'minimal brain dysfunction.' 1937: Charles Bradley discovered amphetamine improved behaviour and academic performance in children. 1955: FDA approved methylphenidate (Ritalin). DSM-II (1968): 'Hyperkinetic Reaction of Childhood.' DSM-III (1980): 'Attention Deficit Disorder (ADD)' with and without hyperactivity - first recognition that inattention could exist independently. DSM-III-R (1987): renamed ADHD. DSM-IV (1994): three subtypes introduced. DSM-5 (2013): age-of-onset criterion raised from 7 to 12 years; adult presentations recognised; co-diagnosis with ASD permitted.

ADHD remains one of the most debated and stigmatised psychiatric diagnoses. Common misconceptions: 'ADHD isn't real,' 'children are overmedicated,' 'adults cannot have ADHD.' Scientific consensus strongly supports the validity and neurobiological basis of ADHD (2021 World Federation of ADHD International Consensus Statement: 208 evidence-based conclusions). Diagnostic rates vary between countries, reflecting awareness and access rather than true prevalence differences. Racial/socioeconomic disparities: Black and Hispanic children in the USA are underdiagnosed and undertreated despite similar prevalence. Rising adult ADHD recognition reflects historical underdiagnosis rather than 'epidemic.'

Active research areas: GWAS have identified multiple common variants; polygenic risk scoring being developed for clinical use. Neuroimaging: longitudinal cortical maturation studies, brain connectivity biomarkers for diagnosis and treatment response prediction. Novel medications: viloxazine, centanafadine, lisdexamfetamine formulations, and investigational compounds. Digital therapeutics: FDA-cleared EndeavorRx (game-based treatment for children); cognitive training apps; neurofeedback (EEG-based). Precision psychiatry: pharmacogenomics (CYP2D6, CYP2C19) for antidepressant/non-stimulant selection. Adult ADHD: growing recognition of sex differences, ADHD+ASD overlap, and late-onset presentations.

APA. (2022). DSM-5-TR. APA Publishing. StatPearls. ADHD. NCBI Bookshelf NBK441838.

StatPearls: https://www.ncbi.nlm.nih.gov/books/NBK441838/ NIMH ADHD: https://www.nimh.nih.gov/health/topics/attention-deficit-hyperactivity-disorder-adhd CDC ADHD: https://www.cdc.gov/ncbddd/adhd/ CHADD: https://chadd.org WHO ICD-11 code 6A05: https://icd.who.int Note: Educational only. Not a substitute for professional care. Content from Wikipedia (https://en.wikipedia.org) 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 contexts, and developmentally inappropriate. ADHD symptoms arise from executive dysfunction. Impairments resulting from deficits in self-regulation such as time management, cognitive inhibition, task initiation, and sustained attention can include poor professional performance, relationship difficulties, and numerous health risks, collectively predisposing to a diminished quality of life and a reduction in life expectancy. It is associated with other mental disorders as well as non-psychiatric disorders, which can cause additional impairment. While ADHD involves a lack of sustained attention to tasks, inhibitory deficits also can lead to difficulty interrupting an already ongoing response pattern, manifesting in the perseveration of actions despite a change in context whereby the individual intends the termination of those actions. This symptom is known colloquially as hyperfocus and is related to risks such as addiction and types of offending behaviour. ADHD can be difficult to tell apart from other conditions. ADHD represents the extreme lower end of the continuous dimensional trait (bell curve) of executive functioning and self-regulation, which is supported by twin, brain imaging and molecular genetic studies. The precise causes of ADHD are unknown in most individual cases. Meta-analyses have shown that the disorder is primarily genetic with a heritability rate of 70–80%, where risk factors are highly accumulative. The environmental risks are not related to social or familial factors; they exert their effects very early in life, in the prenatal or early postnatal period. However, in rare cases, ADHD can be caused by a single event including traumatic brain injury, exposure to biohazards during pregnancy, or a major genetic mutation. As it is a neurodevelopmental disorder, there is no biologically distinct adult-onset ADHD except for when ADHD occurs after traumatic brain injury.

Content from StatPearls / NCBI Bookshelf Attention hyperactivity disorder (ADHD) is a psychiatric condition that has long been recognized as affecting children's ability to function. Individuals suffering from this disorder show patterns of developmentally inappropriate levels of inattentiveness, hyperactivity, or impulsivity. Although there used to be two different diagnoses of Attention Deficit Disorder vs. Attention Deficit Hyperactivity Disorder, the DSM IV combined this into one disorder with three subtypes: predominantly inattentive, predominantly hyperactive, or combined type. The symptoms begin at a young age and usually include lack of attention, lack of concentration, disorganization, difficulty completing tasks, being forgetful, and losing things. These symptoms should be present before the age of 12, have lasted six months, and interfere with daily life activities in order to be labeled as 'ADHD.' This must be present in more than one setting (ie, at home, school, or after-school activities). It can have large consequences, including social interactions, increased risky behaviors, loss of jobs, and difficulty achieving in school. ADHD must be considered within the context of what is developmentally and culturally appropriate for a person. It is considered a dysfunction of executive functioning, predominantly a frontal lobe activity. Therefore, patients with ADHD show disability not only in attention and focus but also in decision making and emotional regulation. Children with ADHD can have difficulty with social interactions, can be easily frustrated, and can be impulsive. They are often labeled as "troublemakers." ADHD is not a new condition and has been called different names throughout history. It was labeled as 'minimal brain dysfunction' in the 1930s and has ever since changed names to ADD and ADHD, respectively. Its prevalence has increased over time, with a seeming spike in the 1950s as school became more standardized for children. It is important to diagnose and treat the disorder at a young age so that the symptoms do not persist into adulthood and cause other comorbid conditions. The treatment for the disorder is mostly related to stimulants and psychotherapy. This review would further shed light upon the causal factors, pathophysiology, and management of ADHD. Etiology The etiology of ADHD is related to a variety of factors that include both a genetic and an environmental component. It is one of the most heritable conditions in terms of psychiatric disorders. There is a much greater concordance in monozygotic twins than dizygotic. Siblings have twice the risk of having ADHD than the general population. Similarly, viral infections, smoking during pregnancy, nutritional deficiency, and alcohol exposure in the fetus have also been explored as possible causes of the disorder. There are no consistent findings on brain imaging of patients with ADHD. The number of dopaminergic receptors has also been implicated in the development of the disorder, whereby research has shown that the receptors are decreased in the frontal lobes in individuals with ADHD. There is also evidence for the role of noradrenergic receptor involvement in ADHD. Epidemiology The subtypes of attention deficit disorders are found to have different rates of prevalence in a group of individuals suffering from the disorders. It is found that the inattentive subtype is prevalent in about 18.3% of the total patients, while hyperactive/impulsive and combined represent 8.3% and 70%, respectively. It is also found that the inattentive subtype is more common among the female population. The disorders (collectively) are found in a 2:1 male-to-female ratio as per different research. It is prevalent in around 3%-6% of the adult population. It is one of the most prevalent disorders found in childhood. There is some evidence that ADHD is more prevalent in the United States than in other developed countries.

Pathophysiology ADHD is associated with cognitive and functional deficits that relate to diffuse abnormalities in the brain. The anterior cingulate gyrus and dorsolateral prefrontal cortex (DLFPC) are found to be small in individuals who are suffering from ADHD. It is thought that these changes account for the deficits in goal-directed behavior. Moreover, activity in the frontostriatal region is also reduced in these individuals as measured by fMRI. It is important to understand these pathophysiological mechanisms so that pharmacotherapy is directed toward them. It is important to remember that ADHD is a clinical diagnosis. There are no standard laboratory or imaging results among patients with ADHD. History and Physical In order to diagnose ADHD, it is very important to take a relevant history of the concerned individual. ADHD is diagnosed in children based on their history, where the children face difficulty in at least 6 of the 9 symptoms as mentioned in DSM 5. Inattentive symptoms include not paying close attention to tasks, missing small details, rushing through tasks, not seeming to listen when spoken to, difficulty organizing things, not finishing work, disliking or avoiding tasks that take sustained mental effort, losing things, or being forgetful. Hyperactive symptoms include fidgeting, feeling like an "internal motor" is always going, leaving their seat, climbing on things, being loud, blurting out answers, talking excessively or out of turn, having trouble waiting their turn, interrupting or intruding on others. These symptoms must be present in multiple settings. In adults, however, these core symptoms may be missing, and they may manifest as other problems, such as procrastination, mood instability, and low self-esteem. They will likely be more impulsive in nature or inattentive, as the hyperactivity symptoms can be better controlled. The symptoms of inattention or hyperactivity will likely be elicited when doing a proper history of childhood but may have been missed. ADHD interferes with functioning and development. This can be included in adults who do not work and is often dismissed in this population. For example, a stay-at-home mom may have difficulty getting her children to school on time, organizing her home, paying attention while driving, etc., which affects her functioning and daily life even though she is not at work or school. It is important to take this into consideration when making a diagnosis. Different scales are used to measure the problems that patients with ADHD are suffering from. One such example is the Brown Attention Deficit Disorder Scale, which includes common areas in which these individuals face difficulty and can be used in adults to identify the disorder. For children, the Vanderbilt ADHD scale is often used as it has both a teacher and parent component. A physical examination, on the other hand, is not as useful in the diagnosis of ADHD, but it can still be used to exclude medical causes such as thyroid problems. It could also help to identify any medical issue that could thereby direct the treatment options. For example, individuals with hypertension may not opt for stimulants as a treatment option. Evaluation ADHD is a disorder that is diagnosed clinically and does not have any specific laboratory or radiologic tests. The neuropsychological tests are not as sensitive for diagnosing the disorder, and hence the disorder should be diagnosed based upon the history of the patient. The evaluation of the patient with ADHD is usually done with different rating scales and multiple informants, who may include the teachers and parents. It is necessary for a clinician to look for other disorders as they may be a cause for the symptoms that a child is exhibiting. It should not be diagnosed in the context of symptoms from another disorder, for example, a psychotic episode or manic episode. DSM 5: Types of ADHD Predominantly inattentive Predominantly impulsive or hyperactive Combination of the above The onset is usually before age 12 Symptoms present at school, work, or home The disturbance causes significant impairment

in social, occupational, and academic functioning. The disorder is not accounted for by any other behavior disorder. Treatment / Management Pharmacological therapy remains the mainstay of treatment for patients who have ADHD. It is divided into two major categories, which fall into stimulants or non-stimulants. Stimulants are further broken into amphetamines and methylphenidates. Both types of stimulants block the reuptake of dopamine at the presynaptic membranes and postsynaptic membranes. Amphetamines also directly release dopamine. Stimulants are the mainstay of treatment for ADHD. They are effective in about 70% of patients. There is a number needed to treat of 2. There are multiple formulations of each subtype of stimulant, including immediate-release and extended-release, long-acting, or sustained release. Side effects of stimulants include changes in blood pressure, decreased appetite and sleep, and risk of dependency. However, there is an increased risk of substance use in patients with ADHD, and studies show treating with a stimulant decreases their overall lifetime risk of substance abuse. Because stimulants are controlled substances, providers often are hesitant to use them. However, repeated evidence has shown how imperative it is to try stimulants in ADHD. There have been concerns regarding stimulant use in patients with seizures. However, recent studies showed that stimulant use for ADHD is safe in epilepsy. There can be an increase in the frequency of tics in patients with ADHD and Tic disorders. Adding alpha agonists may help to reduce tics. Of the non-stimulant option, there are also two types: antidepressants and alpha agonists. Within the antidepressant category, atomoxetine is the best known and works as a selective norepinephrine reuptake inhibitor. It is known to be effective in many trials as a treatment option for ADHD, though not nearly as effective as stimulants. It also has minimal antidepressant effects. It is often used in children who don't tolerate stimulants or have anxiety. Other antidepressants include bupropion, which targets dopamine and norepinephrine, and TCAs, which are the last-choice options. These work by targeting norepinephrine. Lastly, alpha agonists such as clonidine and guanfacine can be used as an effective treatment for ADHD. However, these are associated with multiple cardiovascular effects like lowering blood pressure, sedation (clonidine more than guanfacine), weight gain, dizziness, etc. They are found to be more effective in younger children than adults. Psychosocial treatment is the other form of treatment that is used for individuals suffering from the disorder. This form of treatment includes psycho-education for the family and patient and cognitive-behavioral training programs designed specifically for the patient to achieve short and long-term goals. Research has found that these training programs prove to be very effective when used along with pharmacotherapy. However, unlike other psychiatric disorders, there is strong evidence for medication management without therapy as being the most efficacious. The FDA has just approved the trigeminal nerve stimulation system for children not on medications. The device generates a low-level electrical pulse, which suppresses hyperactivity. No diet has been found to improve ADHD. Differential Diagnosis It is important to differentiate ADHD from other clinical disorders as it can have symptoms that may overlap with them. Mood disorders such as depression and anxiety can be misdiagnosed in a patient with ADHD as these symptoms (inatt... Fresquez-Chavez KR, Fogger S. Reduction of opiate withdrawal symptoms with use of clonidine in a county jail. J Correct Health Care. 2015;21(1):27–34. *Gamo NJ, Arnsten AF. Molecular modulation of prefrontal cortex: rational development of treatments for psychiatric disorders. Behav Neurosci. 2011;125(3):282–296. Gourlay SG, Stead LF, Benowitz NL. Clonidine for smoking cessation. Cochrane Database Syst Rev. 2004;(3):CD000058.

Gowing L, Farrell M, Ali R, White JM. Alpha2-adrenergic agonists for the management of opioid withdrawal. Cochrane Database Syst Rev. 2016;3:CD002024. 2008;25(3):260–271. *Waldon K, Hill J, Termine C, Balottin U, Cavanna AE. Trials of pharmacological interventions for Tourette syndrome: a systematic review. Behav Neurol. soluble in water, freely soluble in methylene chloride, chloroform, and alcohol; slightly soluble in acetone; and insoluble in ether. The molecular structure is shown in Figure 33.8b–1. Atenolol may be chemically described as benzeneacetamide, 2-[4- [2-hydroxy-3-(1-methylethylamine)propoxy]phenyl]ethanamide. The molecular formula is C14H22N2O3. Atenolol has a molecular weight of 266.34. It is a relatively polar hydrophilic compound with a water solubility of 26.5 mg/mL at 37°C and a log partition coefficient (octanol/water) of 0.23. It is freely soluble in 1N hydrochloric acid (300 mg/mL at 25°C) and less soluble in chloroform (3 mg/mL at 25°C). The molecular structure is given in Figure 33.8b–1. Nadolol is chemically described as 2R,3S 5-[2-hydroxy-3-3(tert- butylamino)-propoxy]tetralin-2,3-diol. Its molecular formula is C17H27NO4. Nadolol has a molecular weight of 309.40. It is a white, crystalline powder that is freely soluble in alcohol, propylene glycol, and ethanol; slightly soluble in chloroform and water; very slightly soluble in sodium hydroxide; and insoluble in acetone, benzene, ether, and hexane. The molecular structure is shown in Figure 33.8b– 1. Pindolol is chemically described as 1-(1H-indol-4-ylox)-3-(1- methylethylamino)propan-2-ol. Its molecular formula is C14H20N2O2. Pindolol has a molecular mass of 248.32. Pindolol is a white to off- white crystalline powder with a faint odor. It is practically insoluble in water, slightly soluble in methanol, and very slightly soluble in chloroform. The molecular structure is shown in Figure 33.8b–1. FIGURE 33.8b–1. Molecular structures of β-adrenergic receptor antagonists. PHARMACOLOGIC ACTIONS Pharmacokinetics The pharmacokinetics of atenolol, metoprolol, nadolol, propranolol, and pindolol are listed in Table 33.8b–1. Absorption. Absorption of propranolol (>95%) and pindolol (95%