I have stopped taking Pristiq 50mg. per day and have been put on Effexor at 225 mg per day - what dosage of Effexor is required to equal 50mg. of Pristiq?
Pristiq and Effexor are very similar but not the same. Pristiq is desvenlafaxine, while Effexor is just venlafaxine. It is very difficult to equate one antidepressant to another in terms of dosage. You were taking the normal therapeutic amount for Pristiq, Effexor can go as high as 375mg so 225 isn't too far off looking at it this way. You are going to experience some withdrawal symptoms from the Pristiq and some side effects as you get use to the Effexor (even though they are similar). Be patient and the Effexor should be working within a month.
I realize this question was from much earlier in the year, but I would like to let you know, that the same thing happened to me. I was on Pristiq 50 mg Extended Release Tablet once a day. I couldn't afford to pay for the medication, so my doctor was giving me his samples. He ran out 2 months ago, and started me on Effexor. The reason for creating Pristiq and the reason it worked so well for me was because it gives the same effectiveness of Effexor, but without the side affects. He now has me on Venlafaxine (Effexor) XR 150 mg, which IS the equivalent to 50 mg of Pristiq. I do notice the side affects more which has a tendency to bring me down a little bit because it makes me very tired at times, but my severe depression and anxiety has still been better than it has been in years.
I'm on a combination of Bupropion (Wellbutrin) 200 mg a day, Clonazepam 2 mg a day, Trazodone 200 mg at night time (its helps with insomnia) and the Effexor, which I take in the morning. I hope, if you haven't been helped yet, this will help a little.
About 55% of a single dose of venlafaxine ER (Effexor XR) is converted to desvenlafaxine (Pristiq). The metabolite of the latter is of little clinical consequence. Both are SNRI's (serotonin-norepinephrine reuptake inhibitors). The ratio of serotonin to norepinephrine reuptake for venlafaxine ER is roughly 1:30, whereas for desvenlafaxine it is 1:16 (for the other SNIR's - duloxetine (Cybalta) it is 1:9 and for levmilnacipran (Fetzima) it is 1:0.6). Keep in mind the venlafaxine ER really does not become fully effective as an SNRI till a dose of 225 mg is reached. At the starting dose of 75 mg it acts as a SSRI. The two are NOT the same drug, but rather the parent compound, venlafaxine, is metabolized to desvenlafaxine. Put differently, if you are taking Effexor XR you are also taking Pristiq, but not vice-versa.
There is no simple equation for converting equivalencies, though one might make an informed guess that if 55% one dose of venlafaxine ER is metabolized to desvenlafaxine, then maybe a little less than twice as much of the former would be needed. It is best to work out with your doctor based on the clinical effectiveness of either compound.
Thanks everyone for all of your replies in trying to figure out the mystery of what is comparable. My psychiatrist and I agreed that the dosing he was headed for and which I reached with Effexor was the max dose and bottom line, was way too much. I had a horrible experience with Effexor because the dosing we went to was too high. I think we decided I probably could have started at 75, gone to 150 and had a similar effect as Pristiq. We went to the max of 325 mg per day and it was actually dangerous because my blood pressure went through the roof, I was hallucinating and every other side effect you read about I had. I ended in June last year when I took myself back to 225 and made an appointment to see him. I walked in his door and he had a taper off the Effexor schedule ready, 18 weeks or free samples of Pristiq and a graduation schedule to get back on it with a promise that between the two of us we would get Pristiq covered.
It took 2 appeals but before the 18 weeks was up, the Pristiq was covered and I have been back on it for over a year and am doing amazingly well. So I guess based on that, there really isn't a need to comment any further unless it's helping someone else in a similar situation. As for me, I am where I want to be with medications that after 15 different ones to treat the chronic depression and General Anxiety disorder have allowed me to function relatively normally. I am still on a cocktail but it is minimal. I now am on 50 mg Pristiq, 7.5 mg of Mirtazapine and up to 5 - .5 mg of clonazepam per day although if I take 3, I'm having a bad day. I am no longer trapped in my house, have no drug hangovers at all, don't have difficulty with sleep, am doing a ton of volunteer work, getting a ton of exercise and am basically controlled and happy. It took 9 years to get here but for those who have read this thread and are having difficulty still finding a cocktail that works for you, keep the faith and you will eventually find what works best for you. Good luck everyone and thanks again. Over an OUT! Paul... :)
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