Venlafaxine

Key facts

• Venlafaxine (sold as Effexor and as generics) is an SNRI, a serotonin-norepinephrine reuptake inhibitor, used for major depressive disorder, generalized anxiety disorder, social anxiety disorder and panic disorder.
• You take it once or twice daily with food; it can take 4 to 6 weeks to reach its full effect.
• At higher doses, venlafaxine can raise blood pressure. Your prescriber should check your blood pressure before starting and periodically as the dose increases.
• Venlafaxine causes severe discontinuation symptoms if stopped abruptly: dizziness, electric-shock sensations, nausea and irritability. In people under 25 it can increase suicidal thoughts, especially early in treatment.

What venlafaxine treats

Venlafaxine treats major depressive disorder, generalized anxiety disorder, social anxiety disorder and panic disorder. It eases persistent low mood, excessive worry and recurring panic attacks.

How venlafaxine works

Nerve cells release serotonin and norepinephrine, chemical messengers involved in mood and alertness, and then reabsorb them. Venlafaxine blocks that reabsorption (reuptake), so more of both stay active between nerve cells. At low doses it acts mainly on serotonin; its effect on norepinephrine grows as the dose rises, which is also when blood pressure is more likely to climb.

Before you take it

• Never take venlafaxine within 14 days of a monoamine oxidase inhibitor (MAOI); the combination can cause serotonin syndrome, which can be fatal.
• Tell your prescriber if you have high blood pressure, heart disease, a seizure history or take blood thinners, other serotonergic drugs or NSAIDs, which raise bleeding risk.
• Your prescriber should monitor your blood pressure, particularly at higher doses, and may lower the dose or stop treatment if it rises significantly.
• Never stop venlafaxine suddenly or skip doses. Its short half-life means withdrawal symptoms can appear within hours of a missed dose; taper down slowly under medical guidance, often over several weeks.

Side effects

Common effects, often easing after the first few weeks: nausea, dry mouth, insomnia, sweating and reduced sex drive.

Stop and seek urgent medical care for any of these:

• New or worsening suicidal thoughts, especially if you are under 25.
• A significant rise in blood pressure, chest pain or a pounding heartbeat.
• Agitation, high fever, muscle twitching or confusion (serotonin syndrome).
• Severe rash, swelling or difficulty breathing.

Safety essentials

• Venlafaxine can raise blood pressure, especially at higher doses; your prescriber should check it regularly throughout treatment.
• It also causes some of the most severe discontinuation symptoms of any antidepressant. Never stop abruptly or skip doses; taper down slowly under medical supervision.
• This class carries a warning for increased suicidal thinking in people under 25. Never combine venlafaxine with an MAOI, and tell every prescriber about other serotonergic medicines you take to avoid serotonin syndrome.

This page is educational and does not replace advice from a doctor or pharmacist who knows your health history.