Am I experiencing Fluoxetine withdrawal?

[DanJ1971]

Hello, I was on a high dose of fluoxetine (60mg) up until May time.
In consultation with my psychiatrist I started on 15mg Mirtazapine and started to reduce my fluoxetine. This was because the fluoxetine seemed to have stopped working and I was feeling very low and anxious.
My reduction of fluoxetine was as follows: 15mg Mirtazapine & 40mg fluoxetine for 4 weeks, then 15mg Mirtazapine & 20mg Fluoxetine for 4 weeks, then 15mg Mirtazapine &10mg Fluoxetine for 4 weeks, then stop the Fluoxetine.
As soon as I started to take the Mirtazapine I started to feel better and that continued up until last monday.
Since then I have been suffering with high anxiety, very low mood, extreme fatigue, lack of appetite, diahorea, and really feeling awful.

My question therefore, is am I experiencing fluoxetine withdrawal and what should I do?
The doc thinks no, as I have followed correct process.
The doc has given me a prescription for Venaflaxin (not taken one yet), and to take the Mirtazapine at the same time (for a short while at least).
Anyone have any experience of this or can offer any wise words?

Thank you.

[panic_down_under]

My reduction of fluoxetine was as follows: 15mg Mirtazapine & 40mg fluoxetine for 4 weeks, then 15mg Mirtazapine & 20mg Fluoxetine for 4 weeks, then 15mg Mirtazapine &10mg Fluoxetine for 4 weeks, then stop the Fluoxetine.

When did you take the final dose of fluoxetine?

My question therefore, is am I experiencing fluoxetine withdrawal and what should I do?

I doubt it is withdrawal. Fluoxetine has a very long half-life, about 6 days for fluoxetine itself and up to 16 days for its active metabolite norfluoxetine which does most of the work. This means it takes up to 30 days for all the fluoxetine to be metabolized and up to 80 days for norfluoxetine. It is therefore essentially self-tapering.

I suspect the mirtazapine isn't working as well as you thought and that the brain changes fluoxetine created are unraveling. Anxiety and depression are symptoms of the atrophy of parts of the two hippocampal regions of the brain caused by high brain stress hormone levels killing neurons in the hippocampus and inhibiting the growth of new ones. Antidepressants and therapy both work by stimulating the growth of new hippocampal brain cells (neurogenesis). The new neurons and the connections they form create the therapeutic response, not the meds, or therapy.

Mirtazapine isn't a classic antidepressant, but mostly a powerful antihistamine. It doesn't stimulate neurogenesis, but works as a potent sedative. Which is all some need, however, it is prone to pooping-out, sometimes within weeks. Also, 15mg is the usual starting dose. Most need to take 30-45mg/day.

The doc has given me a prescription for Venaflaxin (not taken one yet), and to take the Mirtazapine at the same time (for a short while at least).

You could take both indefinitely, as you could have fluoxetine and mirtazapine. The drug interaction guidelines claim there is a danger of serotonin syndrome, but this is incorrect. Unlike SSRIs, SNRIs and TCAs mirtazapine has little if any effect on serotonin synthesis, expression or reuptake.

PS:

0.5mg lorazepam as needed

The import part of the prescription is the "as needed". Benzodiazepines can also trigger atrophy of the hippocampi and block the effectiveness of antidepressants as when taken daily for any length of time (Wu X, 2009; Boldrini M, 2014). This doesn't mean you shouldn't take the lorazepam at all for unrelieved anxiety is also bad, but take it only when you need to, not as a just in case preventative.

[DanJ1971]

Hi, thanks so much for the reply.
My final dose of Fluoxetine was approximately 25th August.
What you say about Mirtazapine makes sense and it was always going to be a bridge medication so I could change to another, in my case Venaflaxin.
I’m worried about taking Venaflaxin tbh as some of the reports seem quite scary. That said, I need something, so I shall make a start later.
Yes, fully understood regarding Lorazepam- I only have when my symptoms are too much and thankfully I don’t, and not do I want, have a dependency here. They are a life saver at times though.
Thanks for the info you have sent

[panic_down_under]

My final dose of Fluoxetine was approximately 25th August.

All of the fluoxetine will have been metabolized now, but you still have about 20% of the norfluoxetine in your system.

I'm worried about taking Venaflaxin tbh as some of the reports seem quite scary. That said, I need something, so I shall make a start later.

I'm not a fan of it either. Despite the claims it isn't really a SNRI so has no intrinsic advantages over the other SSRIs. But it could be the right med for you. Unfortunately, finding the most effective still comes down to trial and error.