Drugs for Attention Deficit Hyperactivity Disorder

Drugs for attention deficit hyperactivity disorder (ADHD) improve attention, impulsivity and hyperactivity by enhancing dopamine and noradrenaline signalling in prefrontal and striatal circuits. They are central stimulants (methylphenidate, amphetamines) and non-stimulants (atomoxetine, guanfacine, clonidine, viloxazine). Medication is one part of a plan that includes behavioural and educational measures.

Mechanism. Methylphenidate blocks dopamine and noradrenaline transporters. Amphetamines block reuptake and also release catecholamines. Atomoxetine blocks the noradrenaline transporter. Guanfacine and clonidine act on alpha-2A receptors.

Efficacy. Stimulants help 70 to 80% of patients, with large effect sizes. Non-stimulants help 40 to 60%, with smaller effect.

Differences. Stimulants act within hours and are titrated by effect. Non-stimulants need weeks, but carry little misuse risk.

• Children 6 years and older, adolescents: methylphenidate first, then lisdexamfetamine or another stimulant if response is poor.
• Adults: lisdexamfetamine or methylphenidate first-line, then dexamfetamine, with atomoxetine second-line.
• Non-stimulants first when there are tics, anxiety, substance misuse risk, or intolerance or contraindication to stimulants.
• Before treatment: blood pressure, heart rate, height, weight, cardiac history, and family history of sudden death or arrhythmia.
• Review: every 3 to 6 months for dose and adverse effects, with a yearly review of continuing need.
• Not routinely used in children under 6 years.

Special groups. Pregnancy: avoid unless essential, with specialist advice. Breastfeeding: methylphenidate gives low infant exposure. Children: monitor growth every 6 months. Older adults: cardiac assessment. Kidney and liver impairment: start low. Regional: access is limited, and diagnosis is often missed, so assessment by a specialist is advised; controlled drug rules limit supply.

Adverse effects. Reduced appetite, insomnia, headache, abdominal pain, irritability, raised blood pressure and heart rate, tics, slowed growth, and rarely psychosis or mania. Misuse and diversion are a risk with stimulants.

Contraindications. Severe cardiovascular disease, uncontrolled hypertension, hyperthyroidism, glaucoma, psychosis, phaeochromocytoma, and monoamine oxidase inhibitors within 14 days.

Interactions. Antihypertensives are opposed, and clonidine can interact with stimulants. CYP2D6 inhibitors raise atomoxetine levels.

Monitoring. Blood pressure and pulse at each dose change and every 6 months, height and weight in children, sleep, mood, and misuse.

Referral and escalation. Chest pain or syncope, psychosis, persistent growth failure, or severe tics.