Venlafaxine
Effexor | Effexor XR
Overview
Venlafaxine is a serotonin-norepinephrine reuptake inhibitor (SNRI) used to treat major depressive disorder, generalized anxiety disorder, social anxiety disorder, and panic disorder.
Indications
- Major depressive disorder
- Generalized anxiety disorder
- Social anxiety disorder
- Panic disorder
Contraindications
- Concurrent or recent use of monoamine oxidase inhibitors
- Hypersensitivity to venlafaxine
Classification
Mechanism of Action
Inhibits reuptake of serotonin and norepinephrine, and weakly of dopamine, increasing monoaminergic neurotransmission. Serotonergic effects predominate at lower doses and noradrenergic effects at higher doses.
Pharmacodynamics
Improves mood and anxiety over weeks of therapy. The active metabolite desvenlafaxine contributes to its effect, and higher doses can raise blood pressure.
Pharmacokinetics
- Absorption
- Well absorbed orally with extensive first-pass metabolism.
- Distribution
- Low protein binding and moderate volume of distribution.
- Metabolism
- Metabolized in the liver by CYP2D6 to the active metabolite O-desmethylvenlafaxine.
- Excretion
- Excreted primarily in urine as metabolites.
- Half-life
- Parent about 5 hours; active metabolite about 11 hours
- Bioavailability
- Approximately 45%
- Protein Binding
- Approximately 27%
Dosage
Typical dosage: 75-225 mg daily (extended-release once daily)
Available Forms
- Tablet
- Extended-release capsule
- Extended-release tablet
Side Effects
Common
- Nausea
- Headache
- Dry mouth
- Insomnia
- Sweating
Serious
- Hypertension
- Serotonin syndrome
- Hyponatremia
- Discontinuation syndrome
Rare
- Seizures
- Serious bleeding
Drug Interactions
Additive serotonergic activity raises the risk of serotonin syndrome and seizures.
Combining with this MAO-inhibiting antibiotic can precipitate serotonin syndrome.
Warnings
Antidepressants increased the risk of suicidal thinking and behavior in children, adolescents, and young adults in short-term studies. Monitor all patients for clinical worsening and emergence of suicidal thoughts, particularly during initiation or dose changes.
Pregnancy
Category C
Toxicity
Overdose can cause serotonin syndrome, seizures, cardiac conduction changes, and CNS depression.
Overdose
Provide supportive care with cardiac monitoring; manage seizures with benzodiazepines. There is no specific antidote and dialysis is not effective.
References
Looking for patient-friendly information? Visit RemedyDoor for easy-to-read guides about this medication.