The mechanism of action of venlafaxine in the treatment of MDD, GAD, SAD, and PD is unclear, but is thought to be related to the potentiation of serotonin and norepinephrine in the central nervous system, through inhibition of their reuptake.

Major Depressive Disorder (MDD), Generalized Anxiety Disorder (GAD), Social Anxiety Disorder (SAD), Panic Disorder (PD)

Major Depressive Disorder: For most patients, the recommended starting dose for Effexor XR is 75 mg per day, administered in a single dose. For some patients, it may be desirable to start at 37.5 mg per day for 4 to 7 days to allow new patients to adjust to the medication before increasing to 75 mg per day. Patients not responding to the initial 75 mg per day dose may benefit from dose increases to a maximum of 225 mg per day. Dose increases should be in increments of up to 75 mg per day, as needed, and should be made at intervals of not less than 4 days. In the clinical studies establishing efficacy, upward titration was permitted at intervals of 2 weeks or more. (See Full Prescribing Information.)

Most common adverse reactions (incidence ≥ 5% and at least twice the rate of placebo): nausea, somnolence, dry mouth, sweating, abnormal ejaculation, anorexia, constipation, impotence (men), and libido decreased.

Hypersensitivity to venlafaxine hydrochloride, desvenlafaxine succinate, or any excipients in the Effexor XR formulation. Concomitant use of monoaminoxidase inhibitors (MAOIs) or within 14 days of discontinuing an MAOI.

Serotonin Syndrome: Increased risk when co-administered with other serotonergic agents (e.g.,SSRIs, SNRIs, triptans), but also when taken alone. If it occurs, discontinue Effexor XR and initiate supportive treatment. Elevated Blood Pressure: Control hypertension before initiating treatment. Monitor blood pressure regularly during treatment. Increased Risk of Bleeding: Concomitant use of aspirin, NSAIDs, other antiplatelet drugs, warfarin, and other anticoagulants may increase risk. Angle-Closure Glaucoma: Angle-closure glaucoma has occurred in patients with untreated anatomically narrow angles, treated with antidepressants. Activation of Mania or Hypomania: Screen patients for bipolar disorder. Discontinuation Syndrome: Taper dose and monitor for discontinuation symptoms. Seizures: Can occur. Use cautiously in patients with seizure disorder. Hyponatremia: Can occur in association with SIADH. (See Full Prescribing Information.)