Clinical Psychopharmacology · Paper A
ADHD pharmacology
ADHDAttention-deficit hyperactivity disorder, a condition of inattention, impulsivity and sometimes hyperactivity.Read more → (attention deficit hyperactivity disorder) is treated mainly with stimulant medicines, which, though it sounds back-to-front, improve attention and reduce overactivity. This concept covers the drugs and the monitoring they need. Two ADHD medications illustrate the split well: one is a stimulant that blocks dopamine reuptake, the other a non-stimulant that works differently, e.g. methylphenidate versus atomoxetine. That mechanism difference drives both the side-effect profile and the misuse potential.
Methylphenidate blocks the dopamine and noradrenaline transporters (the pumps that recycle these transmitters back into the nerve); amphetamines also push more of them out. Atomoxetine is a non-stimulant that blocks only the noradrenaline pump. Guanfacine is an alpha-2A receptor agonistA drug or chemical that activates a receptor to produce an effect.Read more →. Before and during treatment, check the heart history, pulse and blood pressure, plus height, weight and appetite, because stimulants can suppress growth and appetite and can raise heart rate or blood pressure. A child on methylphenidate whose growth chart plateaus in weight gain over several months is a recognised pattern, not a coincidence. Clinically, height and weight need tracking at every review, not just symptom control. Among modified-release methylphenidate preparations, the OROS (osmotic-release) formulation is the most tamper-resistant: its delivery mechanism is harder to defeat by crushing or dissolving than other modified-release brands, which matters given stimulants' misuse/diversion potential. Planned medication-free breaks ('drug holidays', e.g. over school holidays) are used when stimulant treatment has slowed a child's growth; pausing the drug allows catch-up growth before restarting. Atomoxetine carries a risk of hepatotoxicity (rare but serious liver injury): patients and families should be warned to report symptoms (e.g. jaundice, dark urine, unexplained nausea), and it is contraindicated or used only with caution in patients with pre-existing liver disease. If an adequate trial of methylphenidate fails to control ADHDAttention-deficit hyperactivity disorder, a condition of inattention, impulsivity and sometimes hyperactivity.Read more → symptoms, the recommended next pharmacological step is a switch to lisdexamfetamine (not simply a dose increase or an automatic switch straight to atomoxetine).
ADHD (attention deficit hyperactivity disorder) is a neurodevelopmental condition marked by inattention, hyperactivity and impulsivity that impairs daily functioning. It matters that the first-line drugs are stimulants, because stimulants improving attention rather than causing overactivity strikes many students as counter-intuitive, and because stimulant prescribing carries real physical monitoring obligations that are easy to underweight next to the psychological side of the diagnosis. Getting the monitoring wrong, missing a rising heart rate or a growth plateau, is a genuine safety failure, which is why this concept is tested so heavily.
A STIMULANT, in this context, is a drug that increases the availability of dopamine and noradrenaline (two neurotransmitters, or brain chemical messengers) at the nerve (the tiny gap between two nerve cells). REUPTAKE is the process by which a nerve cell recycles a neurotransmitter back into itself after release, ending its effect; a REUPTAKE INHIBITOR blocks this pump, leaving more neurotransmitter available in the synapse for longer. A NON-STIMULANT drug still raises noradrenaline or acts on a receptor, but without the stimulant class's amphetamine-like properties.
Methylphenidate is a stimulant that blocks both the dopamine transporter and the noradrenaline transporter (the reuptake pumps for each), raising synaptic levels of both. Amphetamines (including lisdexamfetamine) do this too, but also actively push extra dopamine and noradrenaline OUT of the nerve terminal, a stronger, dual mechanism. Atomoxetine is a non-stimulant that selectively blocks only the noradrenaline transporter, leaving dopamine reuptake largely untouched, which is why it lacks meaningful misuse potential. Guanfacine is a non-stimulant alpha-2A adrenergic receptor (it activates a specific noradrenaline receptor subtype directly), working through an entirely different route again.
Stimulants can suppress appetite and, over months, growth in children, and can raise heart rate and blood pressure in patients of any age. This means height, weight and appetite must be tracked at every review visit, e.g. a child on methylphenidate whose growth chart plateaus in weight gain over several months is showing a recognised, expected-to-be-caught pattern, not an incidental finding to be dismissed. Before starting any stimulant, a personal and family cardiac history, baseline pulse and baseline blood pressure are required, because stimulants are relatively contraindicated in significant pre-existing cardiac disease.
Consider a seven-year-old newly diagnosed with and no cardiac history: methylphenidate is typically first-line, started at low dose and titrated, with height, weight, pulse and blood pressure checked at every dose change and at least every six months thereafter. Now consider a teenager with the same diagnosis who has a history of prescription stimulant misuse in an older sibling at home: an extended-release, harder-to-misuse formulation, or atomoxetine specifically because it lacks misuse potential, becomes the more sensible first choice, even though methylphenidate might otherwise be preferred on efficacy grounds alone.
Anxiety disorders can mimic inattentive-type , since anxious children also appear distracted, but the underlying driver, worry rather than a core attention deficit, changes treatment entirely toward psychological therapy rather than a stimulant. Autism spectrum disorder frequently co-occurs with ADHD and can also independently produce attention difficulties, so diagnosis needs a full developmental history, not just a symptom checklist. Substance misuse in an older teenager can produce hyperactivity or poor concentration that mimics ADHD but resolves with abstinence rather than stimulant treatment.
Diagnosis in the UK follows NICE guidance (NICE NG87, attention deficit hyperactivity disorder: diagnosis and management), requiring a comprehensive assessment covering symptoms across at least two settings (e.g. home and school), developmental history, and screening for coexisting conditions, rather than a single questionnaire score. Before starting a stimulant, baseline investigations include height, weight, pulse, blood pressure and a cardiovascular history; an (electrocardiogram, a heart tracing) or cardiology referral is considered only if that history raises concern, not as a routine screen for every patient.
NICE recommends stimulant medication, methylphenidate first-line, as part of a package that also includes environmental modifications and, in children, parent-training programmes; medication alone is not considered adequate management. Atomoxetine or guanfacine are used when stimulants are unsuitable, poorly tolerated, or where misuse risk is a specific concern. Ongoing monitoring per the Maudsley Prescribing Guidelines in Psychiatry and NICE includes height and weight every six months, and pulse and blood pressure at every dose change, continuing for as long as the medication continues.
If a vignette gives a growth chart plateau, a family history of cardiac disease, or a family history of stimulant misuse, the exam is testing whether monitoring or drug choice should change, not whether the diagnosis is still correct.
Stimulants (methylphenidate, amphetamines) block or reverse dopamine and noradrenaline reuptake and are first-line for , but they demand ongoing growth and cardiovascular monitoring, while atomoxetine and guanfacine offer non-stimulant alternatives with different mechanisms and different risk profiles.