Switching from Sertraline to Fluoxetine???

Posted , 12 users are following.

I was on 50mg of Sertraline, I have gone ‘cold turkey’ without any withdrawal symptoms. 

My GP did not specify how long after stopping the Sertraline, I should start the Fluoxetine.

Has anyone any previous experience with switching, how long should I wait?

(I’m 22, if that matters)

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17 Replies

  • Posted

    I would start straight away, because the effects will take a while to kick in
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  • Posted

    Hello Erin when I have changed from one antidepressant to another my doctor has had me cut back on the one I am on and add the new one at the same time. But if I were you I would call your doctor and see what he wants you to do. How long have you been off the Sertraline? But if you are completely off all antidepressants you will start to feel the effects of it before long. Hope this helps. Please keep us posted. Diane
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  • Posted

    hi erin,

    when you were on 50mg sertraline daily (which is a low dose) then your body should have eliminated it to about 99% after about 10days as sertraline has a half-life of approximately 24hours and with a daily intake of 50mg you would reach a steady state and about 100mg as a max. concentration. After passing of 10 times half-life almost everything is out of the system.

    Since fluoxetine has a much higher half-life (approximately 96 hours) a switch from fluoxetine to sertraline would be considered more critical as from sertraline to fluoxetine. Since both meds are serotonin reuptake inhibitors one wants to make sure to not add a too high concentration of SSRIs to the system. So with SSRIs that have about the same half-life one can decrease the dose of one med and start with the new med at the dose which is the biochemical-equivalent (not the mg!).

    Normally when SSRIs are introduced one would start at a lower dose and then increase it incrementally until the effects are within the expectation.

    Since you've been off the sertraline for 4 days now that would mean that you have about a quarter of your steady state dose left in your system and withdrawal symptoms could still appear later on. yet it is depending on how long you took sertraline. if only for a few weeks then you will probably not experience severe withdrawal symptoms.

    if you're waiting for another week you can definitely safely start with fluoxetine. otherwise if you experience withdrawal symptoms while introducing fluoxetine you might mistake these as a side-effects of the fluoxetine yet in fact you can't know whether it's from sertraline or fluoxetine. this is why i recommend to wait for sure that you don't have withdrawal from sertraline and then introduce fluoxetine.

    do you mind me asking why you're switching from sertraline to fluoxetine?

    - did the sertraline not generate the effects you were hoping for?

    - or did you have side-effects?

    - what is your indication (depression, anxiety, ...?, how strongly affected is your daily living by your symptoms?)

    - how long did you take sertraline? it can take up to 8 weeks for the effects to kick in. sometimes an increase in dosage can do the trick. although one should always take only as much as necessary.

    kind regards,


    ps: i ask these questions because in my opinion antidepressants are overprescribed and many people start with them at a young age for various, often not severe enough reasons, take them for years and then have trouble coming off the medication. then they're diagnosed with relapsing episodes, yet often these are withdrawal/adjustment symptoms, and are told they have to take the medication for life.


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    • Posted

      Thank you. You have been very helpful. I have been on and off different medications for years, to try and find the right one. I have been on Sertraline for nearly 10 months and have not found it helpful with combating the depression. It has also caused a lot of weight gain and as I have a history of Eating Disorders, my increased weight has made me more anxious an depressed. So I am switching back to a medication that I know works better for me in terms of weight and helps with my depression at a higher dose.
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    • Posted

      I was prescribed the medication for various mental health issues, depression being one.

      I have been told that I will be on medication for life to better manage my mental health issues, which I have has symptoms of since the age of 14.

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    • Posted

      Hi Dr.D, I'm so glad you mentioned your theory that people get prescribed anti-depressants early and too often, and then are told they will be on them for the rest of their lives. I have experienced this exactly, I've been on anti-depressants for 15 years and the Dr. that prescribed my first one told me I would 'probably' be on them for the rest of my life. I have been on most, if not all, anti-depressants out there (except the ones my insurance doesn't cover). I don't feel like I have gotten much benefit from them.  In fact, I have definitely gotten worse over time. I slowly. very slowly, came off of my anti-depressants in 2010 and was immediately suicidal. I went straight to the emergency room once I knew I was on the brink because I had formulated a plan. So, I have been on my meds again ever since. I agree with you that it is hard to come off these meds. I would go even further and say that if you are on them for a long time, I think they change the chemistry of your brain. I personally feel like a living experiment because there are no long-term studies regarding the changes in a person's brain over long-time use of these drugs, especially in combination with other anti-depressants, anti-psychotics, and anti-anxiety meds. 

      Anyway, I came on here with a similar question about switching from zoloft to prozac. I've tried both many times, but I've been so depressed lately I knew I needed a change (my belief is that your body/brain get tolerant to certain drugs as time goes by and they don't work well anymore - I don't know if this is true, just my experience.

      My doctor gave me no instruction on how to switch this time. I was on 200mg of Zoloft per day & he prescribed me 40mg of prozac. So, it's been 2 days and I haven't taken any Zoloft (and don't feel the normal side effects when i missed a dose in the past - like fuzzy head, i call it sandbox head).  And I started taking the Prozac in its place. I feel like I should have done this differently.

      I feel a rush of an adrenaline-type feeling on the Prozac, maybe energy. But it is somewhat uncomfortable, but not uncomfortable enough that I don't want to take it.  I take alot of other medications and vitamins, so it's hard to figure out how the meds are interacting with each other.

      I'm going to call my pharmacist, who is really great. Let me know what your thoughts are on switching quickly like I did, and if you think I should still take some of the Zoloft with the Prozac.


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    • Posted

      dear hopefully,

      thanks for reaching out. i am glad to give you my opinion on the switch you are currently doing.

      first i have to make you aware that you should not take zoloft and prozac together as they are both SSRIs and if you take them together you could end up with serotonin syndrome which can be fatal. considering the fact that you took the max. dose of sertraline and are now prescribed fluoxetine (prozac) at a dose above the RDA you should definitely not take them together!

      now about the switch:

      1) it is not uncommon to switch from sertraline to prozac, prozac has a bit of a stronger affinity to norepinephrin transporters than sertraline but a bit less affinity to dopamin transporters and it acts on 3 5-HT receptors compared to 1 (sertraline) plus it acts on at least 7 other receptors (adreno, acetylcholinergic, histamine) in comparison to 3 (sertraline).

      having said that, prozac has a more broad spectrum efficacy than sertraline (zoloft). but for that reason also the potential to cause more side effects.

      2) what i find a bit odd with your switch is that you switch from one to another in no time (no cross taper).

      this can work but contains the risk that you experience side effects which you then cannot match to zoloft withdrawal or prozac ingestion. 

      since prozac works on more receptors than sertraline i would have expected to start with a low dose there as this can create quite severe side effects.

      of course one can do it like this but it seems very likely you'll have to go through some rough weeks.

      another problem is that if you feel like the side effects are too much you can not just go back to sertraline as prozac has a very long half life and you need to wait for the concentration to drop until you take sertraline again, this is also to reduce the risk of serotonin syndrome.

      in cases like yours i feel like the doctors you have seen do not really deal with your problem but rather prescribe some pills, which hardly deals with the root of your problem. of course i don't know about the dynamics of your therapeutic relationship nor do i know you. but i carry a lot of hope that people can get better if one is willing to work at the root of the problem.

      if you like i would be interested in your history. you can PM me for that if you want.

      kind regards,


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    • Posted

      Okay I'm taking Zoloft 50 mgs on a daily basis. But during my menstrual cycle I take 100 mgs because I really need it otherwise I am a raging lunatic with my husband and am overly jealous. However it's taking a big affect on my memory and I'm misplacing things. Can't concentrate on one thing and finish it or forgetting. Also trouble swallowing when I get overwhelmed. I'm concerned. So I have fluoxetine 20 mgs that the Dr had prescribed when I had wanted to switch but I was scared because of side effects since diabetes runs in the family. But I'm willing to try.... Because if what I'm feeling about concentration etc. Can I start from one day to the next???? Is. That wise? Last dose was yesterday of serataline Zoloft 100 mgs

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    • Posted

      hi capricorn,

      the equivalent dose of fluoxetine to 100mg sertraline would be 40mg and respectly 50mg sertraline equals to 20mg fluoxetine. in theory since both medications target the same transmittersystem (serotonin) you could switch from one day to the other. however these both meds also act on different receptors, fluoxetine acts on the same receptors as sertraline plus a few more but with other affinities. so it is likely you will get some symptoms until the fluoxetine fully works. there is no way to say how severe these will be. in the case of a switch in the same class i normally recommend to go with the cross taper. this way you decrease the dose of sertraline whilst increasing the dose of fluoxetine. here is how i would recommend it:

      Day  - Sertraline - Fluoxetine

      1         75mg          10mg

      2         75mg          10mg

      3         50mg          20mg

      4         50mg          20mg

      5         25mg          30mg

      6         25mg          30mg

      7           0mg          40mg

      about the side effects (diabetes), this is normally a problem when people get obese because of the drugs. so if you keep your weight under fluoxetine that would be a rare possibility.

      the increase in dosage during your menstrual cycle is because your hormons make you go haywire, right? you have to keep in mind that fluoxetine has a longer half life than sertraline and therefore it might not make sense to adjust the dose anymore for the menstrual cycle. anyway this suggests some sort of hormonal imbalance that might have another cause. are you taking contraceptives? these can cause imbalances and could explain why you act so hormonal when you have your days.

      why were you prescribed the antidepressants in the first place? for pms?




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    • Posted

      Hi Dr

      I was prescribed 50 mg Sertraline OD for 5-6 months in 2019. I stopped taking my prescription in August and I am pretty sure I made quick and unsupervised withdrawal. Which isnt good and I ended up having issues.

      I started Tinnitus and ED. First I kept ignoring it until recently I decided to consult my GP. He has prescribed Sertraline again !!!!!

      Now at this stage I am finding difficult to have courage to start the same med again which bothered me alot. What are the chances I end up again like this ? Cant be there any herbal alternative like at Holland and Barret. Why can’t I have Fluoxetine ? There are many questions which GPs are least bothered to address because of lack of time.

      I would really appreciate if ppl guide through their experiences.


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    • Posted

      hello shahzad,

      am i getting it right that you quit sertraline cold turkey and then got tinnitus and erectile dysfunction!?!

      with every medication you have to decide if the benefits outweigh the side effects or risks.

      from your description i cannot get for what condition (complex of symptoms) your GP prescribed sertraline. can you clarify what your chief complaint is?

      i suggest to talk to your GP and do not let you be bothered by "the lack of time". if you have questions the GP shall take the time to give you the answers you need. otherwise the appointment may not be of any benefit as you may not take the medicine he prescribed or have to consult again. so rather do it once but right.

      at that point i can not tell whether fluoxetine or herbal remedies would be a better solution as i would need more information on your complaint.

      kind regards,


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