Venlafaxine

Brand Name:Effexor XR

Prescription needed: Yes

What is this drug used for?

Venlafaxine is most commonly used to treat symptoms of depression, generalized anxiety disorder and social anxiety disorder. It has also been used to treat symptoms of hot flashes and in some pain conditions.

When you are feeling symptoms of depression or anxiety, the chemicals in your brain are not working as well as they should or you may not have the correct amount of a certain chemical to keep things in balance. One of these chemicals is called serotonin, also known as one of the “feel good” chemicals that lighten our mood and make us feel less anxious.

Venlafaxine is different from other antidepressants like amitriptyline/nortriptyline (TCA) or citalopram/sertraline/paroxetine (SSRI) in how it works and side effects. It belongs to a class of drugs that increases the levels of different chemicals (serotonin, norephinephrine, dopamine) in the brain to help decrease the feelings of depression or anxiety.

Is there any reason not to take this drug?

You should not take this drug if you are allergic to venlafaxine. Tell your doctor if you have or have ever had (or anyone in your family has or has ever had):

  • a problem with alcohol or drug abuse
  • feelings of worsening depression or suicidal
  • a condition called bipolar disorder
  • seizures
  • problems with your kidney or liver
  • problems with sex drive, ability or orgasm
  • heart disease
  • high blood pressure
  • glaucoma
  • problems with a decreased amount of salt (sodium) in your blood

What about possible side effects?

The most common side effects are:

  • nausea
  • feeling agitated, anxious or excited
  • shaking hands that you cannot control
  • sweating more than usual
  • headache
  • dizziness
  • feeling weak
  • having trouble sleeping, nightmares
  • high blood pressure (usually at higher doses and in people who are at risk)
  • decrease/increase in sex drive; delayed or no orgasm (usually at higher doses and less often when compared to other similar drugs for depression or anxiety)

These side effects are usually related to dose, the use of other medications and other factors (e.g. older age, other medical conditions). As well, some of these symptoms tend to go away within a few weeks of starting treatment and, in most cases, aren't serious enough to cause people to stop taking venlafaxine. Talk to your doctor or pharmacist about whether you have any risk factors that may make you more sensitive to these side effects. Contact your doctor if these symptoms continue or become worse.

Less common and possibly severe side effects include:

  • seizures (rare and a lower risk compared to other similar drugs used for anxiety or depression)
  • low sodium in the blood (older people on water pills are at greater risk)
  • rare cases of hepatitis (inflammation of the liver) have been reported – call your doctor immediately if you have your skin or eyes turn yellow.
  • changes in vision
  • weight loss

This is not a complete list of side effects. If you are concerned about these or other unusual symptoms while taking this medication, ask your doctor and/or pharmacist for more information and advice.

Health Canada has issued a special advisory that says people of all ages who take newer antidepressant drugs may experience behavioural and emotional changes that may increase the risk of suicide. [See other information section]

Read: Health Canada advises Canadians of stronger warnings for SSRIs and other newer anti-depressants

What if I am taking other drugs?

Always provide your doctor with a list of all other drugs you are taking (including over-the-counter medications and herbal/natural products) as they may interact and may change the safety or effectiveness of either drug. Tell your doctor specifically if you are taking any of these drugs as these are the most common interactions and he/she may need to make changes or monitor you more closely:
  • phenelzine, tranylcypromine, moclobemide and other MAO-I inhibitors – avoid the use of these drugs together. Must wait 1-2 weeks after stopping one before you can start the other. Talk to your pharmacist or doctor.
  • amphetamine-like drugs, methylphenidate, L-tryptophan, selegeline, sibutramine, sumatriptan, dextromethorphan, St. johns wort, amitriptyline, imiprimine, desipramine, nortriptyline, buspirone (may increase your chances of having side effects such as high blood pressure, rapid heart beat, sweating, shaking hands, fever, feeling excited, confusion)
  • other medications for depression or anxiety (increased chances for similar side effects)
  • cimetidine (can see higher levels of venlafaxine in your blood and increase your chances of having side effects)
  • amiodarone, quinidine, erythromycin, clarithromycin, risperidone, haloperidol, propafenone, sotalol (increases your chances of having heart rhythm side effects)

This is not a complete list of drug interactions. Ask your doctor or pharmacist to review your list of medications.

Other information:

If you are taking this medication for depression or anxiety: It takes several weeks (4-6 weeks) before this medication will even start to work. Do not stop this medication if you don’t feel it is working. Your doctor will follow you and adjust the dose over time to find the right dose. Sometimes people feel worse in the beginning and want to stop their medication. This is usually due to side effects which tend to go away with time. However, if you feel any of the following symptoms, contact your doctor right away:

  • new or worsening feelings of depression
  • thoughts of suicide
  • extreme worry
  • agitation or panic attacks
  • aggressive behavior
  • acting without thinking
  • severe restlessness
  • frenzied abnormal excitement
  • any other sudden or unusual changes in behavior

Children: Very little information on the use of this drug in children. Not recommended for those under 18 years of age.

Seniors: Can be used but may need to take a lower dose, especially at the start of therapy as this age group may have a higher chance for side effects.

Pregnant women: Safety not established. Not treating the depression is often worse than the possible effects of the medication. Talk to your doctor.

Women who are nursing: Has been used but you need to talk to your doctor first. There is little information on the safety.

People who drive or operate machinery: Should not do so until they know the impact this drug has on them personally as it can cause dizziness, weakness and blurred vision.

Alcohol: You should avoid alcohol as it may increase your chances of having side effects of this drug.

Overdose: If you experience convulsions, have a slow or irregular pulse or lose consciousness, immediate medical attention is required. Call 911 or have someone do it for you.

Stopping the drug: Do not stop taking this drug until you have discussed it with your doctor. Stopping abruptly may cause withdrawal symptoms that feel like flu symptoms (flu-like, insomnia, nausea, off-balance, tingling sensations, feeling anxious/nervous/agitated).

If you miss a dose: Take the next scheduled dose. Never double dose.

Storage conditions: Closed container; cool, dry location away from excess moisture (not in the bathroom); always out of reach of children.

Dietary precautions: None