What is venlafaxine?

Venlafaxine hydrochloride (brand name Effexor) is a medication approved for treating anxiety and depression, including generalized anxiety, panic disorder, social anxiety, and major depressive disorder.

Venlafaxine HCL also has off-label uses, meaning as non-FDA approved treatment for specific conditions. Doctors prescribe venlafaxine for hot flashes and neuropathy, as well as attention-deficit/hyperactivity, obsessive-compulsive, and post-traumatic stress disorders.

How does venlafaxine work?

Venlafaxine is from a class of medications called SNRIs (serotonin-norepinephrine reuptake inhibitors). SNRIs work by inhibiting serotonin and norepinephrine reuptake in the brain, thereby increasing these mood-enhancing chemicals’ levels. SSRIs (selective serotonin reuptake inhibitors), a similar medication, only work on serotonin and not norepinephrine.

Venlafaxine takes four to six weeks to build up in your system and reach full effectiveness. For this reason, it is critical to take the medication exactly as prescribed. Venlafaxine comes in both immediate and extended-release forms. Some key points to remember when taking this medication include:

  • If you miss a dose, take it as soon as you remember, unless it is almost time for the next dose
  • Do not take two doses at once due to the risk of overdose
  • Taking the medication with food can help prevent nausea
  • Do not stop taking if it does not seem to work in the first few weeks; allow time for your body to adjust
  • Do not stop taking the medication cold-turkey, or risk withdrawal symptoms

Venlafaxine side effects

Venlafaxine does have potential side effects, ranging from mild to concerning, though many people do not experience any. Some mild side effects tend to improve over time. Common side effects include:

  • Stomach problems like nausea, loss of appetite, constipation, diarrhea, or dry mouth
  • Tiredness, fatigue, insomnia
  • Tremor or shaking
  • Headaches
  • Nervousness and anxiety
  • Dizziness, blurred vision
  • Excessive sweating
  • Sexual problems

Less common side effects are more concerning. If you experience any of the following side effects, contact your healthcare provider.

  • Elevated cholesterol
  • Overactive bladder
  • Increase in heart rate or blood pressure
  • Unexpected weight gain or loss
  • Skin rash, blisters, hives

If you have trouble breathing or experience swelling of the mouth, lips, tongue, or throat, seek medical attention immediately. These are signs of a severe allergic reaction.

Infrequent but dangerous side effects include:

Serotonin Syndrome: Too much serotonin accumulating in the body can cause an altered mental state such as hallucinations. A racing heartbeat, extreme changes in blood pressure, fever, or muscle spasms and twitching indicate serotonin syndrome.

Mania or Manic Episodes: Feelings of euphoria are not normal or the goal of taking Venlafaxine. Unusually grand ideas combined with reckless behavior, racing thoughts, and severe trouble sleeping are signs of mania.

Hyponatremia: A drop in sodium levels can be life-threatening, especially for the elderly. This condition may cause headaches, weakness, or muscle cramping. Confusion or trouble thinking are also indicators. In severe cases, hyponatremia can cause seizures.

Abnormal Bleeding: Venlafaxine might increase the risk of bruising or bleeding, especially if taken with anti-inflammatory drugs. Warning signs are vomiting blood, bleeding from the gums, changes in your periods that include heavy bleeding, or nose bleeds of longer duration.

Pneumonia: Venlafaxine has the potential to inflame the air sacs of the lungs, causing shortness of breath and painful cough with or without mucus.

Eye Problems: Venlafaxine can bring on vision changes, eye pain, enlarged pupils, or bulging eyes.

Suicidal Thoughts: In extreme cases, venlafaxine can produce or increase suicidal thoughts in children or young adults. Monitor children and young adults closely when they begin to take this medicine for unusual behavior changes, like aggression or violent impulses.

Seek emergency medical care for any of the above conditions.

Venlafaxine withdrawal

Sudden withdrawal from venlafaxine can also cause symptoms, including:

  • Anxiety, irritability
  • Excessive sweating
  • Tiredness, restlessness, insomnia
  • Headaches, dizziness
  • Tremors, shaking, confusion, unusual dreams
  • Vomiting, nausea, diarrhea

Gradually reducing the dosage is recommended to prevent these side effects.

Medical conditions

People with certain medical conditions should not take venlafaxine due to the risk of side effects. These medical conditions include:

  • Heart disease, high blood pressure, high cholesterol
  • Diabetes
  • Narrow-angle glaucoma
  • Liver or kidney disease
  • Thyroid issues
  • Low sodium
  • Epileptic or have had seizures
  • Bipolar disorder

Drug interactions

Some medications interact negatively with venlafaxine, resulting in decreased effectiveness of venlafaxine or unwanted side effects. Tell your doctor if you take any of the following types of drugs:

  • MAOIs (monoamine oxidase inhibitors)
  • Other depression/anxiety drugs
  • Opioids or other pain medication
  • Blood thinners
  • Heartburn medication
  • Regular use of anti-inflammatory OTCs like ibuprofen
  • Mood-altering supplements/herbs like St. John’s Wort

Venlafaxine overdose

It is possible to overdose on venlafaxine, so following dosage instructions is crucial for people who take the medication. As mentioned earlier, the medication works by increasing the levels of serotonin in the brain. Too much of this chemical leads to serotonin toxicity and the risk of Serotonin Syndrome, with all its side effects.

Venlafaxine also blocks sodium and potassium channels and, in high doses, can set the stage for cardiac arrhythmia.

What should I avoid when taking venlafaxine?

Venlafaxine may cause tiredness or affect your ability to think, make decisions, or react quickly. Do not drive or engage in activities that require mental alertness until you know how venlafaxine affects you. Drinking alcohol can exacerbate dizziness, tiredness, or trouble concentrating when taking venlafaxine and should be avoided.

Key takeaways

  • Venlafaxine treats anxiety and depression and has off-label uses as a treatment for hot flashes, other psychological disorders, and neuropathy
  • Take venlafaxine exactly as prescribed or risk unwanted and potentially serious side effects
  • Venlafaxine can cause or increase suicidal thinking in children and young adults. They should be monitored closely while on this medication
  • Be sure to inform your doctor of your medical history, including all prescription and not prescription drugs and health conditions