Can I take Fluoxetine and Venlafaxine together?

You should not take fluoxetine and venlafaxine together unless specifically instructed and closely monitored by a specialist.

Both fluoxetine and venlafaxine work by increasing serotonin levels in the brain. When used together, their effects add up (an additive effect).

Additionally, fluoxetine can slow down the way your liver breaks down venlafaxine, causing the levels of venlafaxine in your blood to rise even higher.

How to know if you're having a drug interaction

You may be experiencing a drug interaction between fluoxetine and venlafaxine if you notice:

• Agitation, restlessness or confusion.

• Shivering, sweating or fever.

• Muscle twitching or stiffness.

• Fast heartbeat.

• Diarrhoea.

• Headache.

• Feeling unusually anxious or overactive.

These can be signs of serotonin syndrome, a rare but serious reaction.

Seek urgent medical help if you have:

• High fever.

• Severe agitation or confusion.

• Seizures.

• Irregular heartbeat.

• Loss of consciousness.

If you are experiencing any of the above symptoms you should:

• Seek emergency medical help (call 999 / go to A&E) if symptoms are severe, worsening quickly, or include high fever, confusion, seizures, or loss of consciousness.

• Do not take any further doses until you have spoken to a healthcare professional.

• Do not stop either medicine suddenly unless a doctor tells you to, as this can cause withdrawal symptoms.

If your doctor is switching you from one to the other, they will usually advise a 'washout' period (a gap of a few weeks) because fluoxetine stays in your system for a long time.

Taking multiple medicines? Our Medicines Interaction Checker helps you check whether your prescriptions, over-the-counter medicines, and supplements are safe to take together. Simply search for your medicines to see potential interactions and what to do about them.

Disclaimer

This information is for general educational purposes only and should not be relied upon as a substitute for professional medical advice. Always consult your GP, pharmacist, or another qualified healthcare professional before making decisions about your medications. Individual circumstances may vary, and only a healthcare professional who knows your medical history can provide personalised guidance.