First of all desvenlafaxine (Pristiq) is an active metabolite of Venlafaxine (Effexor). Most articles say there is no difference between the two. Pfizer came up with Pristiq when the patent for Effexor ran out so they could market it as an expensive novel new drug. There are no studies that say Pristiq is any different than Effexor yet many people say they are different. And the gene test ChangeMyMind had puts Pristiq in the green and Effexor in the red.
https://www.pharmgkb.org/pathway/PA166014758
According to this Venlafaxine (Effexor) Produces 5 Metabolites.
Two pass the blood brain barrier, Venlafaxine and 0-desmethylvenlafaxine (Pristiq)
The 5 melatoblites could all cause side effects because there are different seratonin and norepinephrine receptors through out the body. They all preform different function ie, blood pressure, sexual, digestive and thus the side effects.
There are not many studies on desvenlafaxine (Pristiq) it is much newer. From what I can tell it has less metabolites and thus few side effects. This would make it true that it is a "cleaned up" up version of Venlafaxine (Effexor). The fact that there is no way that venlafaxine could enter the blood brain barrier as it does with Effexor suggest there may be a difference in effectiveness. All the studies done to date say there is no difference in effectiveness but many people claim there is a big difference.
Personally I seemed to do better on Pristiq but with the same side effects.
I am no psychoparmacoligist but the best I can tell from the chemistry and with limited information on Pristiq there is a difference in effectiveness and in side effects.
Quote:
Desvenlafaxine is the major active
metabolite of venlafaxine
O-desmethylvenlafaxine (desvenlafaxine) is the major
active metabolite of venlafaxine and has similar
pharmacological activity to that of venlafaxine. Both
venlafaxine and desvenlafaxine contribute to the
pharmacological effect of venlafaxine.3
Venlafaxine is metabolised to desvenlafaxine
by cytochrome P450 2D6 (CYP2D6). Desvenlafaxine
is not metabolised by CYP2D6 and is excreted
unchanged or after conjugation.
Using desvenlafaxine rather than venlafaxine avoids
CYP2D6 metabolism. Theoretically, desvenlafaxine has
lower potential than venlafaxine for drug interactions
with substrates and inhibitors of CYP2D6. However,
this does not appear to confer any particular advantage
to desvenlafaxine — the product information for
venlafaxine notes that dose adjustment is not required
when venlafaxine is used with drugs that inhibit or are
metabolised by CYP2D6.3
No evidence that desvenlafaxine
is more effective than venlafaxine
or other antidepressants
No studies have been powered to directly compare
the efficacy of desvenlafaxine with venlafaxine or any
other antidepressant. An indirect comparison was made
|