Venlafaxine (Trade name: Effexor) is an antidepressant in the serotonin norepinephrine reuptake inhibitor (SNRI) class used in the treatment of major depressive disorder and anxiety disorders.
Absorption | Well absorbed by GI tract |
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Distribution | Volume of distribution is 7.5±3.7 |
Metabolism | Extensively metabolized in the liver, and desvenlafaxine (O-desmethylvenlafaxine, ODV) is the only major active metabolite. |
Elimination | Renal (primary) |
Half-life | Venlafaxine: 5 hours ODV: 11 hours |
Substrate of (Metabolized by) | CYP 2D6 and 3A4 to desvenlafaxine (o-desmethylvenlafaxine) an active metabolite |
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Induces | |
Inhibits | Weak inhibitor of 2D6 |
Generic name | Venlafaxine Regular/Immediate Release | Venlafaxine Extended Release |
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Tradename | Effexor IR | Effexor XR |
Half-life | 5 hours | 13-14 hours |
Dosage Strengths | 25 mg, 37.5 mg, 75 mg, and 100 mg tablets | 37.5 mg, 75 mg, 150 mg capsules |
Starting Dose | 25 mg PO TID | 37.5 to 75 mg PO daily for 1 week (increase by no more than 75mg q4 days) |
Therapeutic Dose | 150-225 mg per day divided BID/TID | 150mg |
Maximum Dose | Maximum dose is 375 mg per day (doses of up to 600mg has been reported[3]) | 225 mg PO daily |
Advantages | Can be dosed once daily since metabolites offer similar duration to Effexor XR | Once daily dosing and lower side effect profile |
Disadvantages | More adverse effects than Effexor XR | - |
Some patients may have severe problems with discontinuation of venlafaxine, compared with other antidepressants. Do not mistake withdrawal symptoms for relapse! Since venlafaxine is noradrenergic, when it is stopped abruptly, it can cause noradrenergic rebound symptoms including brain fog, dizziness, and sensations of “electric shocks.”