Venlafaxine
Venlafaxine is a serotonin-norepinephrine reuptake inhibitor (SNRI) used for major depression, generalised anxiety disorder and panic disorder. Originally launched as Effexor, it now has authorised generics widely available in immediate-release and extended-release forms.
- Chemical formula
- C17H27NO2
- CAS number
- 93413-69-5
- ATC code
- N06AX16
- Molecular weight
- 277.40 g/mol
- Drug class
- Serotonin-norepinephrine reuptake inhibitor (SNRI)
- Also known as
- Effexor, Efexor, Venlafaxine XR
What is it?
Venlafaxine is the first SNRI introduced into clinical use, approved by the FDA in 1993 and marketed as Effexor by Wyeth (now Pfizer). It was a landmark drug because it broke the SSRI monopoly on serotonergic antidepressant therapy and offered both monoamine pathways at one molecule. Authorised generic venlafaxine and venlafaxine XR are widely available; the molecule is on the WHO Essential Medicines List.
Mechanism of action
Venlafaxine inhibits the reuptake of both serotonin and norepinephrine at the synapse, with a dose-dependent profile: at low doses (≤75mg) it acts mainly on serotonin like an SSRI, while at higher doses (150mg+) the norepinephrine effect becomes substantial. Therapeutic effect develops over 2–6 weeks. The pharmacologically active metabolite desvenlafaxine extends the action and is itself marketed separately as Pristiq.
Pharmacokinetics
Venlafaxine is well absorbed after oral administration with bioavailability of approximately 45%. The terminal half-life of the parent compound is ~5 hours and of the active metabolite desvenlafaxine ~11 hours. Hepatic metabolism is via CYP2D6 with significant first-pass effect. Steady state is reached in about 3 days. The XR formulation allows once-daily dosing where the immediate-release form requires twice or three times daily dosing.
Indications
Venlafaxine is approved for major depressive disorder, generalised anxiety disorder, social anxiety disorder and panic disorder. Off-label uses include menopausal vasomotor symptoms (hot flashes), neuropathic pain and post-traumatic stress disorder. It is generally considered when an SSRI has been ineffective or when stronger antidepressant action is needed for severe cases.
Safety profile
Common adverse effects include nausea (most prominent in the first weeks), dry mouth, sleep disturbance, increased sweating, headache and sexual dysfunction. Dose-related hypertension is a class-specific concern at higher doses (>150mg/day) and warrants blood pressure monitoring. Venlafaxine has a particularly notorious discontinuation syndrome — abrupt cessation produces dizziness, sensory disturbances and flu-like symptoms — and tapering is essential.
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Frequently asked questions
How is venlafaxine different from duloxetine? ▾
Both are SNRIs, but venlafaxine has a shorter half-life (5h parent, 11h metabolite vs ~12h for duloxetine) and a notable dose-dependent profile (SSRI-like at low doses, true SNRI at higher doses). Duloxetine has stronger evidence in chronic pain indications. Discontinuation syndrome is more pronounced with venlafaxine. The choice between them depends on indication and individual tolerance.
How should venlafaxine be tapered? ▾
Venlafaxine should always be tapered gradually — typically reducing the dose by 75mg or 37.5mg every 2 weeks rather than stopping abruptly. The discontinuation syndrome (dizziness, sensory disturbances, flu-like symptoms) is more pronounced than with most other antidepressants because of the short half-life. According to the prescribing information, tapering is essential even after short-term use.
Will venlafaxine raise my blood pressure? ▾
Dose-related blood pressure increase is a recognised effect, particularly at doses >150mg/day. According to the prescribing information, baseline blood pressure should be checked before starting and monitored periodically during treatment, with dose reduction or alternative therapy if hypertension develops.
The information on this website is provided for reference and educational purposes only. It does not replace consultation with a qualified healthcare professional.