What you need to know about venlafaxine (Effexor)
It is a serotonin-norepinephrine reuptake inhibitor (SNRI). It is used to treat major depressive disorder and anxiety disorders, and specifically generalized anxiety disorder (GAD), panic disorder, and social anxiety disorder.
This article will look at the uses and risks associated with venlafaxine.
Here are some key points about venlafaxine. More detail is in the main article.
- Venlafaxine is used to treat major depressive disorder and anxiety and panic disorders.
- It is a serotonin-norepinephrine reuptake inhibitor.
- It is used off-label to treat migraine, diabetic neuropathy, and hot flashes.
- Adverse effects may include worsening symptoms of depression and nausea and vomiting.
How it works
Venlafaxine is a commonly used antidepressant drug.
Venlafaxine is an SNRI. It works by increasing and regulating the levels of two different neurotransmitters in the brain. These are norepinephrine, also called noradrenaline, and serotonin.
At low doses, venlafaxine prevents serotonin reuptake. This means that it leaves more serotonin in the system. At higher doses, it inhibits both serotonin and noradrenaline reuptake.
What are norepinephrine and serotonin?
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.
- increases the heart rate
- triggers the release of glucose from energy stores
- boosts blood flow to the skeletal muscles
Serotonin helps control a number of processes within the brain. These include mood and emotions, anxiety and aggression, sleep, appetite, memory, and perceptions.
Serotonin and norepinephrine are thought to play an important role in controlling people's sense of well-being.
Venlafaxine, under the trade name Effexor, appeared on the American market in 1993, as a treatment for depression.
It is used to treat:
- major depressive disorder
- generalized anxiety disorder (GAD)
- social anxiety disorder
- panic disorder
Some doctors prescribe the drug "off-label" for:
"Off-label" means that the drug has not been approved to treat these conditions, but that physicians take responsibility for prescribing it, especially in cases where no other treatment is effective.
How to take it
Venlafaxine is available:
- as a tablet, taken two to three times a day with food
- as an extended-release (XR) capsule, taken once a day, in the morning or evening, with food
Under the name Effexor, it is only available as the XR version. Generic versions are available in both immediate release and XR forms.
It should be taken around the same time every day.
The doctor will advise about dosage. People with liver or kidney problems will have a lower dose.
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 generalized anxiety disorder (GAD), obsessive-compulsive disorder (OCD), panic disorder, post-traumatic stress 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.
Worsening symptoms of depression
Patients with major depressive disorder may experience a worsening of depression, agitation and other symptoms, including thoughts of suicide, especially at the beginning of the treatment
Those caring for these patients are urged to monitor carefully for these signs and to contact a physician at once if they occur.
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
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.
Not everyone can use this drug.
The patient must let the doctor know about:
- any other conditions
- whether or not they are or may be pregnant
- if they are breastfeeding
- what other drugs they use.
Seizure disorders: Venlafaxine should not be taken by patients who experience seizures.
MAOIs: People who have recently been using an older anti-depressant, known as a monoamine oxidase inhibitor (MAOI), such as Parnate or Nardil, should wait at least 14 days before using Venlafaxine. Interactions have led to serious adverse effects.
Allergies: Anyone who is allergic to its ingredients should not take it. These include venlafaxine hydrochloride, gelatin, titanium dioxide, hypromellose, iron oxide, ethylcellulose, and cellulose.
Glaucoma: Anyone with a history of glaucoma should let their doctor know about this first.
Pregnancy: 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.
Breastfeeding: As the drug can pass into breast milk, mothers taking venlafaxine should talk to their doctor before breastfeeding.
Diet: The medication should be taken with food, but there are no specific dietary restrictions, unless a doctor advises otherwise.
Alcohol: This can add to the drowsiness that the drug can cause.
Age: Venlafaxine is not approved for use by anyone under the age of 18 years.
In those aged 18 years and under, it has been linked to weight gain and, like other depressants, an increase in suicidal thinking.
However, there are very few options for treating those aged 18 years and under, so it is sometimes prescribed "off-label."
It has been found to increase the risk of suicidal thinking, especially in children, teenagers, and young adults.
Missing a dose or taking too much
Just missing one dose may trigger dysphoria, which is a state of anxiety, depression, or unease.
A missed dose should be taken as soon as the person remembers to take it, but if it is nearly time for the next dose, they should skip the missed dose.
No more than one extended-release capsule should be taken in one day.
Taking too much can lead to the following symptoms:
- dizziness, nausea, and vomiting
- dilated pupils
- muscle pain
- feeling hot and cold
- changes in heartbeat
If anyone takes too much venlafaxine, someone should call their local poison control center for advice on 1-800-222-1222. If the person collapses or stops breathing, call 911.
Like all medicines, venlafaxine should be stored in a locked cabinet, out of the reach of children.
It is important also to keep the doctor informed of any other medications, supplements, and health conditions the user might have.
People who are using venlafaxine should attend all their medical appointments, because the doctor will need to monitor for blood pressure and other signs.
If you wish to stop taking this medication, you should do so gradually and under medical supervision, because withdrawal symptoms can occur.
Any unused medication should be returned to the doctor or pharmacy.