Drug interactions
Atomoxetine + Fluoxetine
Severity: Major
Atomoxetine and Fluoxetine: major interaction.
Last updated Sources: US FDA label
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
Fluoxetine strongly inhibits CYP2D6, the main enzyme clearing atomoxetine, so atomoxetine concentrations can increase several-fold. This increases adverse effects such as raised heart rate and blood pressure, insomnia and possible QT effects.
What this interaction means in plain words
Atomoxetine and Fluoxetine can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for.
Atomoxetine belongs to Central Nervous System; Fluoxetine belongs to Central Nervous System.
Why it happens
CYP2D6 inhibition by fluoxetine reduces atomoxetine clearance, giving exposure similar to that in poor metabolizers.
What to do
Start atomoxetine at a low dose and titrate slowly, adjusting as in labeling for strong CYP2D6 inhibitors. Monitor heart rate, blood pressure and ECG in patients with cardiac risk factors.
What to ask your pharmacist
- Does the benefit of taking both outweigh the risk in my case?
- Do I need any blood test, ECG or other check while on both?
- What early warning signs should I watch for, and what should I do if they appear?
Pro+ members
Unlock the full page
Create an account and start a Pro+ trial to unlock the full management advice for Atomoxetine and Fluoxetine, the additional notes, the evidence detail and the whole-prescription interaction checker.
- Full clinical management advice
- Additional notes
- Evidence detail
- Interaction checker for a whole prescription
Try Pro+ free for 7 days on the web. No card needed.
References
Other interactions of Fluoxetine
- Fluoxetine + Isocarboxazid Contraindicated
- Fluoxetine + Mavacamten Contraindicated
- Fluoxetine + Methylene blue Contraindicated
- Fluoxetine + Phenelzine Contraindicated
- Fluoxetine + Pimozide Contraindicated
- Fluoxetine + Rasagiline Contraindicated
Other interactions of Atomoxetine
- Atomoxetine + Isocarboxazid Contraindicated
- Atomoxetine + Linezolid Contraindicated
- Atomoxetine + Phenelzine Contraindicated
- Atomoxetine + Procarbazine Contraindicated
- Atomoxetine + Rasagiline Contraindicated
- Atomoxetine + Selegiline Contraindicated
Frequently asked questions
Can I take Atomoxetine with Fluoxetine?
MediHelp rates the interaction as major. Atomoxetine and Fluoxetine can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for. Fluoxetine strongly inhibits CYP2D6, the main enzyme clearing atomoxetine, so atomoxetine concentrations can increase several-fold. This increases adverse effects such as raised heart rate and blood pressure, insomnia and possible QT effects.
How serious is the interaction between Atomoxetine and Fluoxetine?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Start atomoxetine at a low dose and titrate slowly, adjusting as in labeling for strong CYP2D6 inhibitors. Monitor heart rate, blood pressure and ECG in patients with cardiac risk factors.
What other medicines interact with Fluoxetine?
MediHelp also lists interactions of Fluoxetine with, for example, Isocarboxazid, Mavacamten, Methylene blue. The full list is on the Fluoxetine page.
Full monographs, dosing and an interaction checker in the MediHelp app
Open the complete reference, check multi-drug interactions and use dosing tools in the MediHelp app.
