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Pristiq vs. Effexor: Differences, similarities, and which is better for you

Notice how Pristiq’s generic name is desvenlafaxine, and Effexor’s generic name is venlafaxine. These drugs are very similar. When Effexor (venlafaxine) is metabolized, it turns into an active metabolite—desvenlafaxine.

Why create a medication that's merely the active metabolite of venlafaxine?

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As you have refereed these medications are very similar in the sense that both antidepressants present a similar mechanism of action, consisting of inhibition of serotonin and norepinephrine reuptake. Altough

binding affinity for serotonin and norepinephrine reuptake pumps is higher for desvenlafaxine than venlafaxine, which theoretically could translate to greater efficacy reference

However the major difference that one can find, at a glance, is the fact that venlafaxine undergoes primarily through a phase I metabolization by the CYP 2D6-mediated oxidative reactions to be converted into O-desmethylvenlafaxine. While desvenlafaxine, on the other hand,

is mainly eliminated unchanged by renal excretion, and to a lesser extent metabolized by phase II enzymes to form desvenlafaxine-Oglucuronide reference

Which lead us to conclude that its biodegradation isn't influenced by the enzymatic system of cytochromes P450 (CYP 2D6).

This has at least two main implications

  1. more suitable for liver diseases and in geriatric patients

since it doesn't require an extensive metabolization by the liver to be ready for excretion

  1. more advantageous in patients with genetic polymorphisms of CYP2D6

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