Venlafaxine, also known by its trade name as Effexor, is an antidepressant. It is the one of the most commonly prescribed antidepressants in the United States.
Venlafaxine belongs to the serotonin-norepinephrine reuptake inhibitor (SNRI) class of drugs. It is used for the treatment of major depressive disorder and anxiety disorders, and specifically for generalized anxiety disorder (GAD) and social anxiety disorder (SAD).
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What is a major depressive disorder?
Major depressive disorder involves a loss of interest in activities that are usually enjoyable.
The Diagnostic and Statistical Manual of Mental Disorders IV (DSM-IV) notes that major depressive disorder features a noticeable and ongoing depressed mood on most days for at least 2 weeks, including a loss of interest or pleasure in most activities.
To be diagnosed with the disorder, the person should, over the 2-week period, experience five or more of the following symptoms:
- Depressed mood
- Significantly reduced interest or pleasure in usual activities
- Noticeable change in weight, appetite, or both
- Sleeping too long or too little
- Slow or agitated movements
- Increased fatigue
- Feelings of guilt or worthlessness
- Slower thinking or difficulty concentrating
- Attempting or thinking about suicide.
Generalized anxiety disorder involves at least three of the following symptoms:
- Restlessness, or feeling keyed up or on edge
- Being easily fatigued
- Difficulty concentrating or mind going blank
- Muscle tension
- Sleep disorder.
Social anxiety disorder is when a person reacts with anxiety, which may be similar to a panic attack, when faced with a social situation involving unfamiliar people.
How does venlafaxine work?
As an SNRI, venlafaxine works by increasing and regulating the levels of two different neurotransmitters in the brain. These are norepinephrine, also called noradrenaline, and serotonin.
Venlafaxine is commonly prescribed for depression.
Norepinephrine is a stress hormone. It affects parts of the brain that relate to attention and response, and it underlies the fight-or-flight response, together with epinephrine.
It increases the heart rate, it triggers the release of glucose from energy stores, and it boosts blood flow to the skeletal muscles.
Serotonin helps to control a number of processes within the brain. These include mood and emotions, anxiety and aggression, sleep, appetite, memory, and perceptions.
The two neurotransmitters, serotonin and norepinephrine, are thought to play an important role in controlling people's sense of well-being.
At low doses, venlafaxine inhibits serotonin reuptake. This means that it leaves more serotonin in the system. At higher doses, it inhibits both serotonin and noradrenaline reuptake.
Uses, precautions and adverse effects
Effexor, or venlafaxine, appeared on the American market in 1993, as a treatment for depression. It is used to treat major depressive disorder, GAD, or SAD.
A number of studies have shown the drug to be safe and effective. One review suggests that it is comparable to other major antidepressants in treating GAD, OCD, panic disorder, PTSD and social anxiety disorder. It is more likely to lead to nausea and vomiting than do the SSRIs.
Before taking venlafaxine, patients should discuss their medical history with their doctor to determine whether the drug is appropriate.
Symptoms of depression may worsen
Patients with major depressive disorder may experience a worsening of depression, agitation and other symptoms, including thoughts of suicide. Those caring for these patients are urged to monitor carefully for these signs and to contact a physician at once if they occur.
A major depressive episode can sometimes be the first manifestation of bipolar disorder, so patients should be screened for bipolar disorder before being prescribed venlafaxine.
Venlafaxine should not be taken by patients with seizure disorders.
People who have recently been using an older anti-depressant, known as a monoamine oxidase inhibitor (MOI), such as Parnate or Nardil, should wait at least 14 days before using Venlafaxine, as serious adverse effects have been observed.
Those who are allergic to its ingredients should not take it. These include venlafaxine hydrochloride, gelatin, titanium dioxide, hypromellose, iron oxide, ethylcellulose, and cellulose.
Venlafaxine has been linked to raised blood pressure in some patients, so regular monitoring of blood pressure is recommended.
Anyone with a history of glaucoma should let their doctor know about this first.
One study, published in the Canadian Medical Association Journal (CMAJ), has suggested that pregnant women who take venlafaxine may be at a higher risk of a miscarriage, so pregnant women should only take it if absolutely necessary.
As the drug can pass into breast milk, mothers taking venlafaxine should talk to their doctor before breastfeeding.
Other common adverse effects
Patients may experience these common side effects:
- Blurred vision
- Dry mouth
- Loss of appetite
- Trouble sleeping
- Excessive sweating
- Irregular bowel movements
Rare side effects include:
- High blood pressure
- High cholesterol
- Serotonin syndrome
- Mental impairment
- Thoughts of suicide
People who are using venlafaxine should not stop suddenly, because this can lead to severe withdrawal symptoms.
Just missing one dose may trigger dysphoria, which is a state of anxiety, depression, or unease. Other effects include tremor, dizziness, nausea and vertigo, headache, hallucinations, impaired concentration, fatigue, and paresthesia, which is a sensation of pricking, tingling, or creeping on the skin.
Venlafaxine should not be given to anyone under the age of 18 years.