CNS Stimulant (ADHD / Narcolepsy) Pregnancy: Avoid — amphetamines associated with premature birth and neonatal withdrawal. Schedule 2 controlled drug; specialist decision only if continuation deemed necessary in pregnancy.

Dexamfetamine

Brand names: Amfexa, Dexedrine

Adult dose

Dose: ADHD: 5 mg twice to three times daily (initial). Range: 20–60 mg/day in divided doses. Narcolepsy: 5–60 mg/day in divided doses

Route: Oral

Frequency: Two to three times daily (morning and early afternoon — avoid evening doses to prevent insomnia)

Max: 60 mg/day

Schedule 2 Controlled Drug — written prescription requirements (HS 28-day supply, no repeat prescriptions). ADHD: start 5 mg 2–3 times daily, titrate weekly by 5–10 mg/day. Avoid afternoon/evening doses — insomnia. Shorter duration of action than lisdexamfetamine — allows timing flexibility but more doses needed. Source: BNF 90; NICE NG87.

Paediatric dose

Dose: Children 6–17 years: 2.5–5 mg once or twice daily (initial). Titrate up weekly. Maximum 20 mg/day (children 6–12 years); 40 mg/day (adolescents 13–17 years) mg/kg

Route: Oral

Frequency: Twice daily (morning and lunchtime)

Max: 40 mg/day (adolescents)

Licensed from 6 years for ADHD in UK. Prescribing must be initiated by specialist (ADHD nurse, consultant psychiatrist, or paediatrician). Drug holidays during school holidays can be considered for children (evidence on catch-up growth effect mixed). Source: BNF for Children 2024; NICE NG87.

Dose adjustments

Renal

No specific dose adjustment. Dexamfetamine is partially renally excreted — alkaline urine reduces excretion and increases plasma levels. Acid urine (e.g. ascorbic acid) increases excretion. Caution in severe renal impairment.

Hepatic

No dose adjustment required — hepatic metabolism does not significantly alter clinical dose requirements.

Paediatric weight-based calculator

Patient weight (kg)

Clinical pearls

Dexamfetamine vs lisdexamfetamine in ADHD: lisdexamfetamine (Vyvanse) is a prodrug that must be enzymatically cleaved to active dexamfetamine in the gut — providing smoother onset/offset and lower abuse potential. Dexamfetamine is immediate-release with faster onset (30–60 min) and shorter duration (4–6 hours) — useful when flexibility is needed (e.g. university students who need 'as-needed' coverage on study days only), or in children intolerant of lisdexamfetamine.
Cardiac screening before prescribing (NICE NG87): history of palpitations, syncope, exertional chest pain, or family history of sudden cardiac death at <40 years of age → refer to cardiology before prescribing stimulants. Check BP and HR before and after dose adjustment. Resting ECG if cardiac risk features identified — not routinely required but recommended if symptoms.
Schedule 2 controlled drug — prescribing rules: only specialist (ADHD consultant, nurse prescriber) can initiate. Cannot be prescribed on FP10MDA (methadone script) — requires standard FP10 with full prescriber details. Written prescription; no phone/fax. 28-day supply maximum. Cannot be prescribed more than 28 days in advance.
MHRA sudden cardiac death: rare but documented risk in children and adults with underlying cardiac disease. Contraindicated with structural heart defects. Screen carefully — ask about family history of cardiac death before 40, own history of syncope, exertional chest pain, palpitations.
Drug holiday considerations: growth suppression is modest but real in children on long-term stimulants. Planned drug holidays over summer (when academic demands are lower) can allow catch-up growth and assessment of whether drug is still needed. Discuss with family and school — many children function well during holidays without medication. Source: BNF 90; BNF for Children 2024; NICE NG87; MHRA SPC Amfexa.

Contraindications

Cardiovascular disease (including structural heart defects, arrhythmias, hypertension — MHRA warning: sudden cardiac death)
Hyperthyroidism
History of drug or alcohol dependence (misuse potential — Schedule 2)
Agitated states or psychosis
Concurrent or recent (14 days) MAO inhibitor use — hypertensive crisis
Glaucoma

Side effects

Appetite suppression and weight loss (universal — take with or after food; monitor growth in children)
Insomnia (take no later than early afternoon)
Increased heart rate and blood pressure
Dry mouth, headache
Emotional dysregulation, irritability (especially on dose wearing off — 'rebound' phenomenon)
Tics (may precipitate or worsen tics in susceptible individuals)
Growth suppression in children (modest — monitor height percentile)
Cardiovascular risk: sudden cardiac death (rare but documented — MHRA requires cardiac screening before prescribing)

Interactions

MAO inhibitors: hypertensive crisis — contraindicated; 14-day washout before starting dexamfetamine
Urinary alkalinisers (antacids, sodium bicarbonate): reduce urinary acidification → increase dexamfetamine reabsorption → higher plasma levels
Urinary acidifiers (ammonium chloride, ascorbic acid): increase urinary dexamfetamine excretion → reduced effect
Antihypertensives: dexamfetamine may counteract antihypertensive effects — monitor BP
Haloperidol, phenothiazines: antagonise amphetamine CNS effects
Lithium: may reduce stimulant effects

Monitoring

Blood pressure and heart rate at baseline, 1 month, 3 months, then 6-monthly
Weight and height (children — every 6 months; plot on growth chart; monitor for growth suppression)
ADHD symptom rating scales (SNAP-IV, Conners) at each review
Sleep quality (insomnia monitoring)
Appetite and food intake at each visit
Tics assessment
Mood and affect (stimulant-induced mood dysregulation)

Reference: BNFc; BNF 90; BNF for Children 2024; NICE NG87 (ADHD); MHRA SPC Amfexa; MHRA cardiac warning for stimulants. Verify against your local formulary and the latest BNF before prescribing.

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways