Drug interactions
Fluoxetine + Lithium
Severity: Moderate
Fluoxetine and Lithium: moderate interaction.
Last updated
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
Combining lithium with an SSRI can increase serotonergic effects and in some cases cause serotonin syndrome or lithium neurotoxicity such as tremor and confusion. Both drugs may also have QT effects, though this is less prominent.
What this interaction means in plain words
Fluoxetine and Lithium can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken.
Fluoxetine belongs to Central Nervous System; Lithium belongs to Central Nervous System.
Why it happens
Additive serotonergic activity, with a possible pharmacodynamic increase in lithium neurotoxicity.
What to do
Monitor serum lithium levels and watch for tremor, confusion and signs of serotonin toxicity, particularly at initiation or dose changes. Obtain an ECG in patients with cardiac risk factors.
What to ask your pharmacist
- Should I take them at different times of day?
- Does the dose of either medicine need to change?
- Is there anything I should avoid, such as alcohol or certain foods, while on both?
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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 Lithium
- Lithium + Thioridazine Contraindicated
- Lithium + Vandetanib Contraindicated
- Aceclofenac + Lithium Major
- Acemetacin + Lithium Major
- Amisulpride + Lithium Major
- Amlodipine-benazepril + Lithium Major
Frequently asked questions
Can I take Fluoxetine with Lithium?
MediHelp rates the interaction as moderate. Fluoxetine and Lithium can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken. Combining lithium with an SSRI can increase serotonergic effects and in some cases cause serotonin syndrome or lithium neurotoxicity such as tremor and confusion. Both drugs may also have QT effects, though this is less prominent.
How serious is the interaction between Fluoxetine and Lithium?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor serum lithium levels and watch for tremor, confusion and signs of serotonin toxicity, particularly at initiation or dose changes. Obtain an 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.
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