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Side Effects of Desvenlafaxine (Pristiq, Khedezla)


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Description: Desvenlafaxine, which is marketed under the brand names Pristiq and Khedezla, is a member of a relatively new class of antidepressant medications called “serotonin/norepinephrine reuptake inhibitors,” or SNRIs. It is indicated for major depressive disorder, bipolar disorder, and other conditions.

Serious Side Effects of Pristiq

Serious side effects from Pristiq can occur, according to Pristiq safety labeling changes (Dec 2013), approved By FDA Center for Drug Evaluation and Research (CDER). Pristiq may cause new or worsened high blood pressure, abnormal bleeding or bruising, low sodium levels in the blood and heart attack. These side effects are relatively rare but quite serious.


Low sodium levels may not cause symptoms initially, so blood tests should be performed at regular intervals when on desvenlafaxine. Additionally, as with all antidepressants, there is an increased risk of suicidal thoughts and behaviors.


One of the most dangerous side effects of the medication is angle-closure glaucoma. A condition in which fluid and pressure within the eye increases, causing pain, vision problems and possibly permanent blindness.

Pristiq and other SNRIs side effects include a serious collection of signs and symptoms called “serotonin syndrome.” Serotonin syndrome may cause: elevated body temperature, increased blood pressure and heart rate, nausea/vomiting/diarrhea, restlessness, muscle stiffness, loss of coordination, hallucinations (seeing and hearing things that are not actually there), confusion, and coma or death.

Common Pristiq Side Effects

According to the Pristiq drug label as reported by the FDA (July 2011), common adverse reactions include:

  • Bigger, dilated, or enlarged pupils (black part of the eye)
  • Decreased appetite
  • Inability to have an orgasm
  • Inability to have or keep an erection
  • Increased sensitivity of the eyes to light
  • Loss of sexual ability, desire, drive, or performance
  • Sleepiness or unusual drowsiness
  • Sleeplessness
  • Less Common Side Effects

    According to the Pristiq drug label as reported by the FDA (July 2011), less common side effects include:

  • Change in taste
  • Continuous ringing, buzzing, or other unexplained noise in the ears
  • Decreased weight
  • Difficult urination
  • Fear or nervousness
  • Hearing loss
  • Increased sensitivity of the eyes to light
  • Jitteriness
  • Lack or loss of strength
  • Loss of taste
  • Understand Your Risks with the Rxight® Genetic Test

    The Rxight® PGx (pharmacogenetic) testing program from MD Labs, is grounded in gene analysis and examines the DNA that interacts with the medication. When your DNA-medication interaction is understood, dose can be adjusted and adverse reactions can be avoided. All it takes is a simple cheek swab of your DNA at a participating pharmacy to measure your individual ability to absorb and process Pristiq, as well as hundreds of other over-the-counter (OTC) and prescription medications across 50 clinically significant medication classes. The results are specifically designed to guide your prescriber in finding the safest and most effective dose based on your unique genetics.

    How Does Pharmacogenetic Testing Work?

    Pharmacogenetic testing is a relatively new field of study that looks at inherited genetic differences in drug metabolic pathways which can affect individual responses to drugs. “Slow metabolizers” of a particular medication have genetically encoded enzymes in the liver which are not as effective at processing and assimilating that drug into the body, thus leading to toxicity or adverse reactions. In contrast, so-called “fast metabolizers” have liver enzymes that process the drug quickly, so that a higher dose is needed to achieve therapeutic benefit. With pharmacogenetic testing, prescribers can adjust medication dosages or find a safer medication based on the your individual genetic profile.


    Contributors to this Article:
    Michael Sapko, MD, PhD; Deborah Kallick, PhD, Medicinal Chemistry

    Read more about Rxight® pharmacogenetics