SSRI question

[MexicanDr]

---

Members don't see this ad.

What is the equivalent dose of 40mg of Paxil in Prozac more or less?

 

[whopper]

I have never seen any data showing an exact equivalent.

I have seen equivalent charts with benzodiazapines. For antipsychotics you could look up the level of D2 blockage to try to figure out what is the equivalent dose--though that is far from an exact science because some antipsychotics work in some and not in others, and they are theorized to work for reasons beyond D2 blockage.

For Citalopram you can merely double the dose to get the equivalent dose of Lexapro.

For SSRIs, this is what I do, and this is an overly simplistic model that has to be taken into consideration with other things---look at the dosage ranges. E.g. for Paxil the top range is 50mg. If you want to cross taper them to another SSRI, strongly consider bringing the person to the top range of the other SSRI.

You mentioned Paxil 40 mg to Prozac. Max dose of Paxil is 50mg. Max dose of Prozac is 80mg. (manufacturer's recommendation). Ok--you could do the old algebraic method---40/50 = x/80 and figure out X.

That is an extremely simplistic model. Real psychopharm is more complicated than that.
http://www.southstaffshealthcare.nhs.uk/services/MMP/formulary/SwitchingChart.pdf

 

[kugel]

What is the equivalent dose of 40mg of Paxil in Prozac more or less?

If we know why you are asking the question, we may be able to provide more information. Are you switching a pt from one to the other? Are you asking about likelihood of side-effects b/w them at "equivalent" doses? Give us some context, and you may get more responses.

 

[Regnvejr]

Given that response level may vary from med to med, the outcome probably is not proportional.

And, given the high level of side effects in Paxil. not much is equivalent in any way with Paxil.

 

[BabyPsychDoc]

Given that response level may vary from med to med, the outcome probably is not proportional.

And, given the high level of side effects in Paxil. not much is equivalent in any way with Paxil.

I agree with Regnvejr. Response level varies widely between different SSRIs, so it is difficult to talk about "proportional doses".

 

[billypilgrim37]

Did nobody else think the reason this question was being asked was because the OP was switching his/her own antidepressant?

 

[pingouin]

Did nobody else think the reason this question was being asked was because the OP was switching his/her own antidepressant?

ding ding ding. 👍

of course, personal medical advice threads are not permitted on SDN so if it turns out that were the case, this thread would cease to exist.

 

[Eyti]

.

 

[whopper]

Yep--that thought did cross my mind--a bit too late. Oops.

I guess my eagerness to teach a student went over some common sense.

 

[Pneumothorax]

Various SSRIs are metabolized by different isozymes of CPY450, and depending upon the genetic makeup of the patient, they will require a higher/lower dose of one SSRI to get a similar effect to the other.

The only apples to apples comparison I can imagine is citalopram to lexapro, because lexapro is the S isomer of citalopram. But I think that the R isomer has some level of activity, so I don't think you can just double citalopram and get the equivalent dose of lexapro.

 

[whopper]

But I think that the R isomer has some level of activity, so I don't think you can just double citalopram and get the equivalent dose of lexapro.

It does have some activity, but for all intents and purposes its hardly anything. I do recall in the comprehensive text of Kaplan and Sadock, and in other sources-the actual activity of the R isomer was mentioned.

 

[RegularNihilist]

Yep--that thought did cross my mind--a bit too late. Oops.

I guess my eagerness to teach a student went over some common sense.

Are there any medical threads on this forum, that could NOT be a well-informed patient asking for advice?

Ridiculous, mind-reading rule.

 

[loveoforganic]

This thread still exists doesn't it? And this thread seems to be pretty obviously motivated by self medication adjustment. Either that or weird, random curiosity.

 

[Pneumothorax]

There are plenty of weird, randomly curious questions I've thought of. Especially when I was taking pharmacology. If I'd asked, people would have thought I was asking for medical advice when I was just really curious. That being said, this was asked by a pre-med student, and it wasn't about mechanisms or anything like that. But I'm willing to give it the benefit of the doubt that they were just curious. Now they know something about pharmacology that they didn't!

 

[Eyti]

There are plenty of weird, randomly curious questions I've thought of. Especially when I was taking pharmacology. If I'd asked, people would have thought I was asking for medical advice when I was just really curious. That being said, this was asked by a pre-med student, and it wasn't about mechanisms or anything like that. But I'm willing to give it the benefit of the doubt that they were just curious. Now they know something about pharmacology that they didn't!

Exactly. People always just jump to conclusions. Ever since I started that class I've been thinking a lot differently and people always jump to assumptions about my own mental state. I'm just extremely curious about that area: the intersection of organic chem, psychology, and biology.

 

[billypilgrim37]

Exactly. People always just jump to conclusions. Ever since I started that class I've been thinking a lot differently and people always jump to assumptions about my own mental state. I'm just extremely curious about that area: the intersection of organic chem, psychology, and biology.

Look at the context. The question was not about equivalent doses of SSRIs. It was about the equivalent dose of a particular regimen with another particular regimen. 95% of the people who ask that question are patients on regimen A wanting to switch to regimen B (or asking because their girlfriend just got switched, and is now crying more, or because they're on regimen A and their friend is on regimen B and they want to know who is most emo, etc.), or a practitioner wanting to switch regimen A to regimen B. The latter has an infinite number of more obvious places to ask that question than an anonymous forum, and the former doesn't. Even a medical student would ask their resident.

Yes, we jump to conclusions, based on evidence that modulates the probability of conditions being true. Do I know this was medical advice? Of course not. Can I make a really strong argument for it? I think so.