Atomoxetine side effects
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Methylphenidate: IR and XL capsules
100% IR
Methylphenidate IR
Methylphenidate (generic) · Ritalin
Duration 4 hrs per dose
50:50 XL
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Methylphenidate · modified-release capsule
Duration up to 8 hrs
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Methylphenidate · modified-release capsule
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Methylphenidate · modified-release capsule
Duration up to 8 hrs
30:70 XL
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Methylphenidate · modified-release capsule
Duration up to 8 hrs
Methylphenidate: XL tablets
OROS 22:78
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Methylphenidate · prolonged-release tablet
Duration up to 12 hrs
25:75 XL
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Methylphenidate · prolonged-release tablet
Duration up to 12 hrs
XL tablet
Affenid XL
Methylphenidate · prolonged-release tablet
Duration up to 12 hrs
XL tablet
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Methylphenidate · prolonged-release tablet
Duration up to 12 hrs
XL tablet
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Methylphenidate · prolonged-release tablet
Duration up to 12 hrs
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Duration24 hrs (once daily)
Onset4–8 weeks for full effect
Doses
10mg18mg25mg40mg60mg80mg100mgLiquid 4mg/ml
Atomoxetine takes 4–8 weeks to reach full therapeutic effect; it is not a "kick-in today" medication. GI side effects are most prominent in the first few weeks. ⚠️ Liver caution and MAOI interaction: these must be checked before starting.
This guide covers common, everyday side effects. See the full list of Atomoxetine side effects, including rarer ones
What helps
- Always take atomoxetine with food; this significantly reduces nausea
- Taking at the same time each day helps your body adapt
- Nausea typically improves substantially after the first 2–4 weeks
ExpectedNausea is very common early on and almost always settles with time and food.
What helps
- Take with or after food to minimise irritation
- If abdominal pain is severe or persistent, contact your prescriber
DiscussPersistent or severe abdominal pain: especially with jaundice or dark urine: should be reported promptly.
What helps
- Eat before your dose when appetite is strongest
- Monitor weight in the early weeks of treatment
- If appetite does not recover after the adjustment period, discuss at your next review
DiscussSustained appetite loss or unintended weight loss should be reviewed.
What helps
- Maintain good fluid intake and adequate dietary fibre
- Regular physical activity supports gut motility
ExpectedUsually manageable with dietary adjustments.
What helps
- Initial irritability or mild anxiety is common as the brain adjusts to increased noradrenaline
- This typically settles significantly by weeks 3–6
- Keep a brief daily note: tracking improvement over time is reassuring
DiscussIf irritability or anxiety is severe or not improving by week 4, discuss dose adjustment with your prescriber.
What helps
- Any new or worsening low mood, thoughts of self-harm, or suicidal thinking should be reported to your prescriber without delay
- This is a known consideration particularly in younger patients: your prescriber is aware and monitoring
WatchDo not wait for a scheduled review if you notice new suicidal thoughts or significant worsening of mood. Contact your prescriber or NHS 111 today.
What helps
- If drowsiness is a problem, try taking atomoxetine in the evening: sedation shifts to overnight
- Avoid driving or operating machinery until you know how it affects your alertness
- Fatigue typically reduces after the first 2–4 weeks
DiscussIf drowsiness affects work, driving, or safety: discuss shifting your dose time with your prescriber.
What helps
- If insomnia occurs with an evening dose, try switching to a morning dose
- A consistent wind-down routine and avoiding caffeine after midday can help
DiscussDose timing adjustment often resolves sleep disruption: discuss with your prescriber.
What helps
- An expected effect of noradrenaline reuptake inhibition
- Your prescriber monitors BP and pulse at every review
WatchPounding or racing heartbeat at rest, chest tightness, or sudden dizziness: contact your prescriber promptly.
What helps
- Stay well hydrated: aim for 6–8 glasses of water daily
- Paracetamol or ibuprofen are safe alongside atomoxetine
ExpectedEarly headaches are common and usually resolve as your body adjusts.
What helps
- Wear breathable, moisture-wicking fabrics
- Stay well hydrated to compensate
- More noticeable early in treatment and usually reduces over time
ExpectedA known noradrenergic effect: uncomfortable but not medically concerning in most cases.
What helps
- More common in adult males
- Stay well hydrated
- Contact your prescriber if this becomes bothersome or worsens
DiscussIf you are unable to urinate at all, this requires urgent medical attention: contact your prescriber or GP same day.
When to speak to your prescriber
Use this guide for any ADHD medication. When in doubt: always make the call.
Green No action needed
- Reduced appetite during the day
- Mild headache in the first week
- Dry mouth
- Feeling more talkative or energised
- Nausea in the first 1–2 weeks
- Mild sleep difficulty while dose timing settles
- Emotional dip as medication wears off (rebound)
- Some stomach discomfort in the first days
Amber Raise at your next review
- Sleep problems persisting past 2–3 weeks
- Significant weight loss or consistent inability to eat
- Feeling emotionally blunted or not yourself
- Low mood, anxiety, or tearfulness
- Irritability affecting relationships or daily life
- New or worsening tics
- Persistent headaches beyond two weeks
- Anxiety that doesn't settle after week 2
Red Urgent: don't wait
- Chest pain, tightness, or irregular heartbeat
- Severe shortness of breath
- Signs of very high blood pressure: severe headache, vision changes, confusion
- Hallucinations or loss of touch with reality
- Thoughts of self-harm or suicide
- Seizures with no prior history
- Allergic reaction: rash, swelling of face/lips/throat, difficulty breathing
Additional cautions: Atomoxetine (Strattera)
- Liver warning: signs of liver problems: yellowing of skin or eyes (jaundice), dark urine, right-sided upper abdominal pain, or unusual nausea with fatigue: require urgent medical attention
- Suicidal thoughts: any new or worsening thoughts of self-harm or suicide should be reported to your prescriber immediately: do not wait for a scheduled review
- MAOI interaction: atomoxetine must not be taken within 14 days of stopping an MAOI antidepressant: dangerous interaction
- Urinary retention: if you are completely unable to urinate, contact your prescriber or GP the same day
For anything in the red column, or if something just feels very wrong: contact your clinical team or NHS 111 today. In an emergency call 999.
You will never be in trouble for checking.
Info
This guide is for general information only. It does not replace medical advice. Always follow your prescriber or pharmacist. Information is UK-based and aligned with NICE guidelines. © 2026 ADHDnotepad: clinician-authored.