|US brand name: Pristiq|
|Generic name: desvenlafaxine|
side effects, dosage, how to take & discontinue, uses, pros & cons, and more
Table of Contents (hide)
- 1. FDA-Approved Uses of Pristiq (desvenlafaxine)
- 2. Off-Label Uses of Pristiq (desvenlafaxine)
- 3. Pristiq (desvenlafaxine) Pros and Cons
- 4. Pristiq (desvenlafaxine) Side Effects
- 5. Interesting Stuff Your Doctor Probably Won’t Tell You about Pristiq (desvenlafaxine)
- 6. Pristiq Dosage and How to Take Pristiq (desvenlafaxine)
- 7. How Long Pristiq (desvenlafaxine) Takes to Work
- 8. How to Stop Taking Pristiq (desvenlafaxine)
- 9. How Pristiq (desvenlafaxine) Works
- 10. Pristiq’s Half-Life & Average Time to Clear Out of Your System
- 11. Days to Reach a Steady State
- 12. Comments
- 13. Pristiq Ratings, Reviews, & Other Sites of Interest
- 14. References
Class: Antidepressant, specifically a Serotonin and Norepinephrine Reuptake Inhibitor (SNRI)
- Major Depressive Disorder (MDD) - Approved 2008
2. Off-Label Uses of Pristiq (desvenlafaxine)
- Hot flashes and other vasomotor symptoms of menopause. Pristiq is undergoing clinical trials for this application, as there’s more money in menopause than mental illness.
- Pretty much everything for which Effexor is approved or used off-label:
- Because it’s works on more than one neurotransmitter, Pristiq is far less likely to poop-out than an SSRI.
- Far fewer drug-drug interactions than Effexor, so if Effexor works for you, but is now a problem because of some other medication(s) you need to take for some other condition(s), Pristiq might be an option.
- Weight gain is less likely than SSRIs or Effexor.
- Sexual side effects are lower than SSRIs for women.
- Just because some of the side effects aren’t as bad for some people doesn’t mean it’s a completely different drug than Effexor
- Especially when it comes to the discontinuation syndrome. That may or may not suck less, but the potential of it happening is no different.
- Weight gain is probably less likely for the same reason as Viibryd.
- Sexual side effects are more likely for men than some SSRIs (say Prozac and Luvox).
- Pistiq has one drug-drug interaction Effexor doesn’t: nicotine.
Like most crazy meds, Pristiq’s side effects are dosage-dependent. The more you take the more likely it is you’ll have any given side effect, and any side effect you do have is going to be worse.
The usual for SNRIs: nausea, headache, nausea, dry mouth, nausea, excessive sweating, nausea, sleepiness or insomnia, nausea, diarrhea or constipation, and nausea. Those side effects typically go away in about two weeks. Weight gain is a lot less likely with Pristiq than SSRIs and Effexor, but with all the nausea and diarrhea you can expect, there may be a reason for that. Sexual side effects are less likely for women due to the effect of norepinephrine, and since Pristiq is more effective on norepinephrine than Effexor, especially at the lower dosages, that means Pristiq is less likely to cause sexual side effects in women at all dosages. It may even enhance sexual desire and response. Unfortunately extra norepinephrine can cause sexual dysfunction in men, so SNRIs like Pristiq, Effexor and Cymbalta can be as bad as, if not worse than SSRIs. While the chances of male sexual dysfunction with a pure norepinephrine-selective reuptake inhibitor (NSRI) like Strattera or reboxetine are lower than SSRIs, because the way the drugs cause the problem are different, it’s a cumulative effect.
Urinary hesitation, high blood pressure, nose bleeds. If you get frequent nose bleeds and/or you bleed like a stuck pig during your period when you never did before, you should call your doctor1.
While Effexor is well-known for causing raging alcoholism, this is much less of a problem with Pristiq. It does happen, just to a much lesser extent. As this person’s experience shows, having it happen with one med does not mean it will happen with the other.
- Dysgeusia. OK, dulling of taste isn’t particularly freaking or weird in the world of crazy meds, but the term isn’t used in PI sheets as often as the vaguer and freakier seeming “abnormal taste.” Plus I like the way dysgeusia rolls off the tongue.
- SSRI/SNRI discontinuation syndrome has been reported when switching from Effexor to Pristiq, so either they did something stupid, or there’s more to Effexor’s particularly hellish version of the discontinuation syndrome than serotonin.
- While smoking has no effect on Effexor, it does affect Pristiq. If you smoke heavily you may need to take more Pristiq and take it twice a day. If you smoke less than heavily you may be hosed, because Pristiq comes in only two sizes.
As Pristiq (desvenlafaxine) comes in all of two sizes, 50mg and 100mg, I can’t really argue with Pfizer/Wyeth’s recommendations of starting with 50mg a day, taken once daily, and that’s it. See for yourself:
2.1 Initial Treatment of Major Depressive Disorder
The recommended dose for PRISTIQ is 50 mg once daily, with or without food. In clinical studies, doses of 50–400 mg/day were shown to be effective, although no additional benefit was demonstrated at doses greater than 50 mg/day and adverse events and discontinuations were more frequent at higher doses.
PRISTIQ should be taken at approximately the same time each day. Tablets must be swallowed whole with fluid and not divided, crushed, chewed, or dissolved. --Pristiq PI sheet
Since nothing above 50mg a day supposedly works, Wyeth makes a 100mg tablet for the hell of it. I’m way behind on gathering data for the efficacy of 50mg vs. 100mg vs. anything more than that. Wyeth did a lot of tests and trials at 100mg, and I suspect that was their target dosage, but the side effects at 100mg sucked too much for people in the usual 6–8 week clinical trials run to get a product approved by the FDA.
As you can see, Pristiq is currently rated safe for up to 400mg a day, just as Effexor is safe to take up to 450mg a day. However: Effexor is extensively metabolized, so the small percentage2 of people who need the high dosage of Effexor because they rapidly metabolize it would not necessarily need the corresponding dosage of Pristiq, because Pristiq is barely metabolized before you piss it out. Of course lots of people need a high dosage of Effexor because Effexor is just a weak-ass drug that, frankly, I’m astonished works at all.
Since the recommended dosage is 50mg a day, there isn’t a smaller pill, and Pristiq comes only in an extended release form, your only official option is to just stop taking it. Obviously that isn’t going to work if you’re taking 100mg a day, where, from the wording on the PI sheet, it reads as if Wyeth assumes you’re going to just stop taking 100mg cold turkey. Buh?
If intolerable symptoms occur following a decrease in the dose or upon discontinuation of treatment, then resuming the previously prescribed dose may be considered. Subsequently, the physician may continue decreasing the dose, but at a more gradual rate. --Pristiq PI sheet
So how much more gradual can you get from 50mg? The standard protocol for withdrawing from an SSRI or SNRI if you have a history of or experience the symptoms of SSRI/SNRI discontinuation syndrome is reducing the dosage by the lowest available pill by however many days the plasma clearance is (scroll down a little if you don’t see it), or one week, whichever is shorter or easier. But what if that doesn’t work for you with Pristiq?
As with all SSRIs and SNRIs you can use Prozac (fluoxetine). Its long-ass half-life of 9.3 days makes SSRI discontinuation syndrome incredibly rare. 20mg of Prozac is approximately equivalent to 50mg of Pristiq. If that can’t happen, or doesn’t work, well, never in a million years would I thought I’d ever write this, but: try using Effexor to help mitigate the symptoms of SNRI discontinuation. If you have some 37.5mg Effexor XR capsules lying around. At least with Effexor you can lower the dosage a bit more gradually, as 75mg of Effexor = 50mg of Pristiq.
Based upon the monoamine hypothesis of depression (i.e. you’re messed up due to an imbalance of one or more of three of the best understood neurotransmitters: serotonin, norepinephrine, and/or dopamine), Pristiq (desvenlafaxine) attempts to balance your brain juices by inhibiting the reuptake (in English: delaying the breaking down and recycling) of serotonin and norepinephrine at their receptors in various (i.e. depending on which studies and books you’ve read and fancy brain scans you’ve looked at) locations in your brain. It may do a lot of other things that address depression, anxiety, other brain cooties and some off-label uses by encouraging the growth of new neurons, affecting hormones and CYP450 genes in your brain, and who knows what else. You also have serotonin and norepinephrine receptors throughout your body, especially in your GI and renal systems, which is why SSRIs & SNRIs are used to treat various conditions like IBS and incontinence. As Pristiq affects norepinephrine more than Effexor, it is more effective for pain and pain-related conditions like fibromyalgia, and the physical pain that accompanies some forms of depression. As Pristiq doesn’t affect norepinephrine nearly as much as Cymbalta, Savella (milnacipran), and some TCAs, it’s never going to get approved to treat pain-related conditions as they are.
Pristiq (desvenlafaxine) has a half-life of 11 hours. It takes about three days to clear out of your system. That’s plasma clearance.
Half-life is the average time it takes for you to process half of the drug’s active ingredient. If a drug has a half-life of around 24 hours and you take a dose of 100mg, you’ll have roughly the equivalent a 50mg dose after one day, a 25mg dose after two days, and so on. The rule of thumb is: multiply the half-life by five and you get how long it is for the dose you took to be cleared from your bloodstream3, so there’s nothing swimming around to attach itself to your brain and start doing stuff. That’s called “plasma clearance.” Complete clearance is a complex equation based on a lot of factors which may or may not: be published in the PI sheet, include personal data like your weight, or even completely figured out by corporate and independent researchers. It usually winds up being 2–5 days after plasma clearance no matter what4, but can take weeks.
Sometimes a drug will clear from your brain and other organs before it clears from your blood.
Steady state is the flipside of half-life. This is when you can expect to get over side effects caused by fluctuating amounts of a medication in your bloodstream. Often, but not always the same amount of time as the plasma clearance above.
I initially thought Pristiq was a patent-extender of Effexor (venlafaxine), much in the same way that Invega (paliperidone) is a patent-extender of Risperdal (risperidone). I was wrong. Sort of. Pharmacologically they are quite different. Desvenlafaxine succinate (the active ingredient of Pristiq) is similar, but not identical to o-desmethylvenlafaxine (the active metabolite of venlafaxine hydrochloride, the active ingredient of Effexor). Plus venlafaxine HCl does stuff, and isn’t just something you take that needs to be converted by your liver into something useful, like Risperdal and Trileptal are. So Pristiq is a different drug than Effexor (venlafaxine); Pristiq is even more different from Effexor than Lexapro (escitalopram) is different from Celexa (citalopram).
But in many ways they are the same drug. Their effect on norepinephrine doesn’t come close to that of Cymbalta, Savella, or several TCAs. They have similar side effects. They are less likely to poop out, and more likely to be effective than an SSRI. Because Effexor is, in a way, two drugs while Pristiq is essentially one, Effexor might be more effective for more people, albeit with a harsher side effect profile and more drug-drug interactions.
I’m reserving my judgment until I do more research. As it is now Pristiq is looking like a failed attempt at being a patent-extender for Effexor, and Pfizer is going to push it as a menopause med, probably with a new name, once they get approval.
|Shirts to swipe from|
Crazymeds’ Clothes Line.
|See more ways to let my |
ADs express your feelings
|at Straitjacket T-shirts.||Shirts, hoodies & more.|
Medicated for Your Protection
Don’t worry about buying one. Windows shop and share the designs you’d like to buy. Do you have anything better to do right now?
Give your overall impression of Pristiq on a scale of 0 to 5. Detailed ratings and reviews are available on the Pristiq Ratings & Reviews Page.
Get all critical about Pristiq
Rating 3.1 out of 5 from 193 criticisms.
Vote Distribution: 33 – 13 – 15 – 17 – 62 – 53
If you’re still feeling judgmental as well as just mental5, please boost or destroy my self-confidence by honestly (and anonymously) rating this article on a scale of 0 to 5. The more value-judgments the better, even if you can criticize my work only once.
Get all judgmental about the Pristiq (desvenlafaxine) Synopsis
Rates 4.1 out of 5 from 112 value judgments.
Vote Distribution: 3 – 3 – 1 – 9 – 54 – 42
Medicine Is The Best Medicine
I <3 Wellbutrin
13.3 Full US PI sheet, Global SPCs & PILs, Other Consumer Review & Rating Sites, check for drug-drug interactions
It’s always a good idea to check for drug-drug interactions yourself. Just because most people in the crazy meds business know about really important interactions (e.g. MAOIs and a lot of stuff, warfarin and everything on the planet) doesn’t mean the person who prescribed your meds told you about them, or the pharmacist has all the meds you take at their fingertips like they’re supposed to. Or they have the time to do their jobs properly when not dealing with complete idiots or playing Angry Farmers on the Faecesbooks.
Medicine Is The Best Medicine stickers
Fuck Depression stickers
PTSD Sucks! stickers
Fuck Bipolar bumper stickers
You don’t have to buy anything. Look around the store. Tweet what you like to your Pinbook Circle. Do you have anything better to do right now?
If you have any questions not answered here, please see the Crazymeds Pristiq discussion board.
||Keep Crazymeds on the air.
Donate some spare electronic currency
you have floating around The Cloud
|Display your mad pride. ||Tell your imaginary friends about Crazymeds. |
Stahl’s Essential Psychopharmacology: Neuroscientific Basis and Practical Applications (Essential Psychopharmacology Series) Third edition by Stephen M. Stahl © 2008 Published by Cambridge University Press.
The Prescriber’s Guide (Essential Psychopharmacology Series) Third edition by Stephen Stahl © 2009 Published by Cambridge University Press.
Clinical Handbook of Psychotropic Drugs 18th edition Adil S. Virani, K. Bezchlibnyk-Butler, J. Jeffries © 2009 Published by Hogrefe & Huber Publishers.
PDR: Physicians’ Desk Reference 2010 64th edition back through to 53rd edition of 1999. Old copies of the PDR come in handy for PI sheets that are no longer available and difficult to find, as well as to track the changes in both indications and adverse effects.1 Especially any of you guys who are bleeding like stuck pigs during your periods. You should have called your doctors last week. Along with lawyers, publicists, and maybe a priest.
2 The current estimates of people who rapidly metabolize - i.e. quickly clear Effexor out of their system and need to take a high dosage of Effexor XR and other once-a-day meds twice a day, is 1-2% of the population. My guess is around 5-7% of the readers of Crazymeds.
3 Based on Julien's calculations from A Primer of Drug Action, the half-life multiplied by five is the generally accepted estimate of how long it takes a single dose of any given drug to be eliminated from the blood stream/plasma of someone with a normal metabolism. That's also the rough estimate for steady stage if they can't get, or won't provide a number for that.
4 For crazy meds. I have no idea what the average complete clearance is for other types of medications. For all I know there are drugs that utterly vanish from your system in under five passes, and others that won't let go of your squishy bits for years after you stop taking them.
5 Thank you! I'll be here all weak. Be sure to tip your content provider. And don't try the veal, it's cruelicious!
If you have any questions not answered here, please see the Crazymeds Pristiq discussion board. We welcome criticisms of the articles, notifications of bad links, site problems, consumer experiences with medications, etc. I’m not always able to write back. Hence I never answer questions about meds via e-mail that are answered by this or other articles. Especially if they have been repeatedly asked on the forum. That’s why we write these damn things. Questions about which meds are best for your condition should also be asked on the forum; because this is a free site, so the price of admission is making things easier for somebody else searching for the same answer. We don’t deal with children on the forum or in private because after doing this for ten years I don’t have the emotional stamina to deal with kids who have brain cooties. How to contact Crazymeds. — Jerod Poore, CME, Publisher Crazymeds (crazymeds.us)
|Last modified on Thursday, 25 September, 2014 at 16:54:13 by JerodPoore||Page Author Jerod Poore||Date created|
|“Pristiq (desvenlafaxine): a Synopsis for the Educated Consumer.” by Jerod Poore is copyright © Jerod Poore||Published online 2012/10/10|
|Citation options to copy & paste into your article:|
|Plain text:||Poore, Jerod. “Pristiq (desvenlafaxine): a Synopsis for the Educated Consumer.” Crazymeds (crazymeds.us). ().|
Pristiq, and all other drug names on this page and used throughout the site, are a trademark of someone else. Pristiq’s PI Sheet will probably have the name of the manufacturer and trademark owner (they’re not always the same company) at or near the very bottom. Or ask Google who the owner is. The way pharmaceutical companies buy each other and swap products like Monopoly™ real estate, the ownership of the trademark may have changed without my noticing. It may of changed hands by the time you finished reading this article.
Page design and explanatory material by Jerod Poore, copyright © 2003 - 2015. All rights reserved.
Keep up with Crazymeds and and/or my
slow descent into irreparable madness boring life. Pick your preferred social media target(s):
Follow me for site updates,
and research & pharm news.
|Wear my Straitjacket||Batshit Crazy Blog|
Crazymeds | Promote Your Page Too||
Follow for site updates and
retweets to cheer you the hell up.
|Play Dress-Up with your Imaginary Friends||Crazymeds: The Blog|
Almost all of the material on this site is by Jerod Poore and is copyright © 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013, 2014, and 2015 Jerod Poore. Except, of course, the PI sheets - those are the property of the drug companies who developed the drugs the sheets are about - and any documents that are written by other people which may be posted to this site will remain the property of the original authors. You cannot reproduce this page or any other material on this site outside of the boundaries of fair use copying without the express permission of the copyright holder. That’s usually me, so just ask first. That means if want to print out a few pages to take to your doctor, therapist, counselor, support group, non-understanding family members or something like that - then that’s OK to just do. Go for it! Please. As long as you include this copyright notice and something along the lines of following disclaimer, I’m usually cool with it.
All rights reserved. No warranty is expressed or implied in this information. Consult one or more doctors and/or pharmacists before taking, or changing how you take any neurological and/or psychiatric medication. Your mileage may vary. What happened to us won’t necessarily happen to you. If you still have questions about a medication or condition that were not answered on any of the pages you read, please ask them on Crazy Talk: the Crazymeds Forum.
The information on Crazymeds pertains to and is intended for adults. While some information about children and adolescents is occasionally presented (e.g. US FDA approvals), pediatric-specific data such as dosages, side effects, off-label applications, etc. are rarely included in the articles on drugs or discussed on the forum. If you are looking for information regarding meds for children you’ll have to go somewhere else. Plus we are big pottymouths and talk about S-E-X a lot.
Know your sources!
Nobody on this site is a doctor, a therapist, or a pharmacist. We don’t portray them either here or on TV. Only doctors can diagnose and treat an illness. While it’s not as bad as it used to be, some doctors still get pissed off by patients who know too much about medications, so tread lightly when and where appropriate. Diagnosing yourself from a website is like defending yourself in court, you suddenly have a fool for a doctor. Don’t be a cyberchondriac, thinking you have every disease you see a website about, or that you’ll get every side effect from every medication1. Self-prescribing is as dangerous as buying meds from fraudulent online pharmacies that promise you medications without prescriptions.
All information on this site has been obtained from the medications’ product information / summary of product characteristic (PI/SPC) sheets and/or medication guides - which is all you get from sites like WebMD, RxList,
NAMBLA NAMI, etc., the sources that are referenced throughout the site, our personal experience and the experiences family, friends, and what people have reported on various reputable sites all over teh intergoogles. As such the information presented here is not intended as a substitute for real medical advice from your real doctor, just a compliment to it. You should never, ever, replace what a real doctor tells you with something from a website on the Internet. The farthest you should ever take it is getting a second opinion from another real doctor. Educate yourself - always read the PI/SPC sheet or medication guide/patient information leaflet (PIL) that comes with your medications and never ever throw them away. OK, you can throw away duplicate copies, but keep at least one, as that’s your proof of purchase of having taken a med in case a doctor doubts your medical history. Plus they take up less space than a bottle, although keeping one inside of a pill bottle is even better.
Crazymeds is not responsible for the content of sites we provide links to. We like them, or they’re paid advertisements, or they’re something else we think you should read to help you make an informed decision about a particular med. Sometimes they’re more than one of those things. But what’s on those sites is their business, not ours.
Crazymeds is optimized for ridiculously large screens and browsers that don’t block ads. I use Firefox and Chrome, running under Windows 72. On a computer that sits on top of my desk. With a 23 inch monitor. Hey, at least you can make the text larger or smaller by clicking on the + or - buttons in the upper right hand corner. If you have Java enabled. Like 99% of the websites on the planet, Crazymeds is hosted on domain running an open source operating system with a variety of open source applications, including the software used to display what you’ve been reading. As such Crazymeds is not responsible for whatever weird shit your browser does or does not do when you read this site3.
No neurologists, psychiatrists, therapists or pharmacists were harmed in the production of this website. Use only as directed. Void where prohibited. Contains nuts. Certain restrictions may apply. All data are subject to availability. Not available on all mobile devices, in the 12 Galaxies Guiltied to a Zegnatronic Rocket Society, or in all dimensions of reality. Hail Xenu!
‘Everything is true, nothing is permitted.’ - Jerod Poore
1 While there are plenty of books to help you with hypochondria, for some reason there’s not much in the way of websites. Then again, staying off of the Internet is a large part of curing/managing the disorder.
2 Remember kids, Microsloth operating systems are like TOS Star Trek movies with in that every other one sucks way, way more. With TOS Star Trek movies you don’t want to bother watching the odd-numbered ones. With Microsloth OS you don’t want to buy and install the even-numbered ones. Anyone who remembers ME and Vista knows what I mean.
3 Have I mentioned how open source operating systems for commercial applications is one of the dumbest ideas in the history of dumb ideas?* I don’t even need my big-ass rant any more. Heartbleed has made my case for me. And that’s just the one that got all the media attention. The very nature of an open source operating system makes security as much of an illusion of anonymity. Before you flip out too much: the domain Crazymeds is hosted on uses a version of SSL that is not affected by the Heartbleed bug. That’s one of the many reasons why I pay a lot of money and keep this site on Lunarpages.
* Yes, I know I’m using open source browsers. I also test the site using the now-defunct IE and Safari browsers. Their popularity - and superiority - killed IE and Safari, so that’s why I rely on the open source browsers. It’s like brand vs. generic meds. Sometimes the generic is better than the brand.