Your doctor has decided to change you from one antidepressant to another. This is a common decision — usually because the current one isn’t working well enough, or the side effects are unacceptable. This page explains what to expect and what to watch for. It is not medical advice — your doctor knows your situation.
Call 000 or go to ED immediately if — during or after a switch — you develop: a high fever, severe muscle stiffness or twitching, confusion, very fast heart rate, severe sweating, or seizures. These can be signs of serotonin syndrome, a medical emergency.
Why a switch might happen
It isn’t working well enough. Up to two-thirds of people don’t respond fully to their first antidepressant. About a quarter of people switched to a second medication achieve full remission.
Side effects are unacceptable. Sexual dysfunction, weight gain, sleep disturbance, or others affecting quality of life.
Pregnancy, surgery, or physical illness means the current drug isn’t suitable any more.
The condition has changed. For example, anxiety symptoms have emerged and a different drug suits better.
How your doctor chooses how to switch you
There isn’t one method — your doctor picks based on the two specific medicines, your situation, and how high the risk would be of stopping the current one suddenly. The four common approaches are:
Gradual taper, then a gap, then start the new one
The safest method — the old medicine is slowly reduced, then there’s a few days with neither medicine, then the new one starts. The "gap" is so the old drug clears your system before the new one is introduced.
Direct switch
Stop one drug; start the other the next day. Only suitable for certain medicine combinations — your doctor will know which.
Cross-taper
The old medicine is gradually reduced while the new one is gradually increased, so for a few weeks you’re on both. Used when stopping the old one entirely would be too risky — for example, if you have severe symptoms.
Long washout (specific medicines only)
Some medicines (particularly an older class called MAOIs and one called fluoxetine) need long gaps — up to 6 weeks — before another medicine can be started safely. Your doctor will explain the timing.
Discontinuation symptoms — what they feel like
When you stop or reduce an antidepressant, you may get temporary physical symptoms as your body adjusts. These usually start within a few days, peak in the first week, and settle over 1–2 weeks. They are not addiction — antidepressants don’t cause craving or compulsive use.
Common discontinuation symptoms: dizziness, "electric shock" sensations in the head or limbs, nausea, flu-like feelings, fatigue, headache, anxiety, irritability, vivid dreams, sleep disturbance.
Symptoms are worse for some medicines than others (venlafaxine and paroxetine are well known for being harder to stop), and gentler taper schedules help. If you’re finding it difficult, talk to your GP — they may slow the taper down.
How to tell discontinuation symptoms from relapse
This is an important distinction. Both can happen during or after a switch, and they need different responses.
Discontinuation symptoms
Depression relapse
Start within hours to days of dose change
Build over days to weeks
Mostly physical: dizziness, nausea, electric shocks, flu-like feelings
Mostly mood & thinking: low mood, hopelessness, loss of interest, slowed thinking
Settle within 1–2 weeks
Persistent and worsening without treatment
Improve quickly if the dose is restarted
May take weeks to improve on treatment
If you’re unsure which it is — contact your GP. Don’t try to work it out alone, especially if your mood is dropping.
When to call your GP (not urgent)
Discontinuation symptoms are severe or not settling after 1–2 weeks
Your mood is dropping or worry/anxiety is building up over days
You’re struggling to take the new medicine because of side effects
You’re tempted to stop one or both medicines on your own — please call first
When to seek urgent help
Call 000 or go to your nearest ED if you develop:
High fever, severe muscle stiffness or twitching, confusion, very fast heart rate, severe sweating, or seizures (possible serotonin syndrome)
Thoughts of harming yourself or ending your life
A sudden severe headache, chest pain, or palpitations
Crisis support — available 24/7 Lifeline — 13 11 14 | Beyond Blue — 1300 22 4636 | 13YARN (Indigenous-led) — 13 92 76 | Suicide Call Back Service — 1300 659 467
Things to do during a switch
Keep taking the medicines exactly as prescribed — don’t skip doses or stop early.
Tell anyone else prescribing for you — pharmacist, dentist, other specialists — about both medicines. Some over-the-counter medicines (including St John’s wort) can interact dangerously.
Avoid alcohol or other recreational drugs during the switch.
Don’t drive if you feel dizzy or sedated.
Keep a simple note of how you feel each day — it helps your GP track whether the new medicine is working.
Be patient. A new antidepressant usually takes 3–4 weeks to start working, and the full effect may take 6–8 weeks.
Common questions
Sometimes — it depends on the medicines. The safest method usually involves a short washout of a few days. For some combinations the gap is much longer (up to 6 weeks). For others your doctor will avoid a gap entirely by cross-tapering. Your doctor will tell you the plan.
Antidepressants generally take 3–4 weeks to start having an effect on mood, and 6–8 weeks for the full benefit. Side effects often come earlier than benefits, which can be discouraging — it’s worth knowing in advance. If you’ve had no improvement at all after 3–4 weeks at an adequate dose, talk to your GP.
No. Addiction means tolerance, drug-seeking and compulsive use — none of those happen with antidepressants. But many antidepressants do cause withdrawal-like symptoms if stopped suddenly, which is why your doctor tapers the dose gradually. These two things are different.
Take the missed dose as soon as you remember, unless it’s nearly time for the next one. Don’t double up. If you miss several doses, call your GP or pharmacist for advice — especially if you’re mid-switch.