Xeljanz Causing Blood Clots in the Lungs

Xeljanz can cause blood clots in the lungs, which can create devastating and sometimes fatal consequences, including a pulmonary embolism. Despite the danger, it was only in July of 2019 that the FDA ordered Pfizer, the manufacturer of Xeljanz, to update the drug's warning label to warn doctors and patients. As a result, hundreds of victims have filed Xeljanz lawsuits, claiming that the drug company failed to adequately warn them of the potential for Xeljanz causing a blood clot in their lungs and demanding compensation for their losses.

The defective drug lawyers at the Shouse Law Office strive to legally represent victims of Xeljanz by helping them file a lawsuit before the statute of limitations has expired. In this article, they discuss:

xeljanz tablets

1. Xeljanz and rheumatoid arthritis

Xeljanz is the brand name of the drug tofacitinib, which treats rheumatoid arthritis, psoriatic arthritis, and ulcerative colitis. It was originally only approved by the U.S. Food and Drug Administration (FDA) in November, 2012, to treat rheumatoid arthritis.1 However, the FDA extended its approved uses to cover psoriatic arthritis in December, 2017,2 and ulcerative colitis in May, 2018.3

The drug is supposed to be for people who have tried other drugs to treat their ulcerative colitis or arthritis, like the drug methotrexate, but who had a poor response to it. However, Xeljanz has especially popular because it can be taken orally in the form of a pill. Earlier treatments for rheumatoid arthritis had to be injected.

Xeljanz works by slowing down the activity of certain Janus kinase, or JAK, enzymes in the body.

JAK enzymes control how the nucleus of a cell interacts with its surroundings, including when or whether the cell replicates itself, grows, and spreads. This can create a problem if JAK enzymes cause cells to grow or spread too quickly. JAK enzymes that overwork and buildup tissue in joints can cause inflammation, bone deterioration, and ruin the joint. The immune system can target this buildup of tissue and attack it, adding to the inflammation and causing more pain and joint problems in a medical condition known as rheumatoid arthritis.

By inhibiting JAK enzymes, Xeljanz can help treat rheumatoid arthritis.

2. Side effects of Xeljanz

Xeljanz is not without risks, though. The drug has some common side effects, including:

  • Sore throat,
  • Fatigue,
  • Sinus infections,
  • Upper respiratory tract infections,
  • High blood pressure,
  • Low white blood cell counts, or neutropenia,
  • Runny nose or nasal congestion,
  • Headaches, and
  • Diarrhea.

Xeljanz can also cause some far more severe side effects, too:

  • Malignancies and cancer,
  • Liver damage,
  • Blood clotting in the lungs, and
  • Pulmonary embolisms.

These side effects can be fatal, and are more likely at high dosage levels of Xeljanz.

blood clot diagram

3. Xeljanz can cause blood clots in the lungs

One of the severe side effects of taking Xeljanz is a risk of a blood clot in the lungs, also known as a pulmonary embolism.

3.1 What are blood clots and how do they reach the lungs?

Blood clots can happen for a variety of different reasons, including:

  • Poor circulation,
  • Broken bones, or
  • Stasis, as the lack of movement can allow blood cells to coagulate.

Most blood clots occur in the deep veins of the legs – those that are far away from the skin and that channel blood from the legs back to the heart and lungs. A blood clot that forms in the legs can dislodge and go with the flow of blood towards the torso. If it reaches the heart or lungs, it can cause serious damage.

3.2 How severe is a blood clot in the lungs?

If a blood clot reaches the lungs, it can block an artery and cause a pulmonary embolism, a serious medical condition that requires emergency medical care.

An estimated 50,000 people die of pulmonary embolisms every year in the United States.4 One medical study found that 26% of people who have pulmonary embolisms and do not receive proper care die from the condition.5 While that estimate is likely too high, due to the fact that only severe pulmonary embolisms could be detected at the time of the study, the condition is still often a fatal one.

Even when a blood clot has reached the lungs and the results were not fatal, the condition can still cause debilitating complications and long-term repercussions.

3.3 Clinical trials link Xeljanz to blood clots in the lungs

In a post-marketing study that was required by the FDA, Xeljanz was found to drastically increase the likelihood of a blood clot forming and then traveling to the lungs to cause a pulmonary embolism, especially when taken at a high dose.

That post-marketing study is Study A3921133.6 A randomized clinical trial, Study A3921133 began on March 14, 2014 and is estimated to be completed in March, 2020. It covers 4,400 participants, all of whom have at least one cardiovascular risk factor, and is designed to compare the efficacy and safety of Xeljanz to a tumor necrosis factor inhibitor drug in people with rheumatoid arthritis. The trial aimed to find out whether Xeljanz was more or less safe for people who have higher cardiovascular risks, and monitored their heart health and whether they developed malignancies or cancer.

Participants taking Xeljanz were further divided into different dosage levels.

Even though the study has not wrapped up, yet, Pfizer intervened on February 19, 2019, to take participants off of the twice daily dose of 10 milligrams.7 The decision was made after Pfizer was notified by the Rheumatology Data Safety Monitoring Board that a disturbingly high number of people in that dosage level were developing blood clots in their lungs and suffering pulmonary embolisms. People taking the high dosage level of Xeljanz were suffering pulmonary embolisms more than five times as often as people taking the tumor necrosis factor inhibitor drug.8 They were also suffering pulmonary embolisms three times as often as other Xeljanz participants in that trial and others like it.9

After the notification, Pfizer shifted people from the twice daily 10 milligram dose to the twice daily 5 milligram dosage level. It announced the change in a press release on February 28, 2019.10

Pfizer's announcement was likely spurred by the FDA's similar announcement about Xeljanz, which warned the public of the potential for a blood clot reaching the lungs after taking the drug. The FDA's announcement came on February 25, 2019.11

4. Symptoms of a blood clot in the lungs

Depending on the size of the blood clot and where it is in the lungs, the symptoms that you can experience can change. Small clots that do not completely block a pulmonary artery can be nearly asymptomatic, as can clots that only compromise a small portion of the lungs.

Larger clots that affect a significant portion of the lungs, though, can cause the following symptoms:

  • Intense chest pain, especially when breathing deeply,
  • Coughing, including coughs that produce blood,
  • Leg swelling, often in the calf area or lower leg,
  • Fever,
  • Sweating,
  • Lightheadedness, dizziness, or feeling faint,
  • Sudden shortness of breath, and
  • Heart arrhythmias.

5. Xeljanz lawsuits against Pfizer for blood clots

attorneys working hard on xeljanz lawsuits
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Hundreds of lawsuits have been filed against Pfizer by people who have taken Xeljanz and suffered from a blood clot that reached their lungs. These lawsuits argue that Pfizer had a legal duty to warn doctors and patients of these risks, but failed to do so.

Doctors and patients both rely on disclosures from drug companies to make healthcare decisions. Doctors use the information from these disclosures to make effective prescriptions that will treat medical problems without producing severe adverse effects. Patients use the disclosures to weigh the pros and cons of a drug and make an informed decision about their health.

However, drug companies understand that disclosing all of the side effects of their drugs can cut into their profits by deterring patients. Covering up or playing down the side effects of a drug can make millions of dollars, providing a strong incentive to make as few disclosures as possible.

The law requires pharmaceutical companies to make reasonable disclosures. If drug companies fail to do so, victims can recover compensation in a lawsuit that proves the drug company failed to adequately warn the public about the dangers of their product.

That failure to warn claim is at the heart of these Xeljanz lawsuits against Pfizer. They seek compensation for:

  • Past and future medical bills,
  • Lost wages and other professional setbacks,
  • Pain and suffering, and
  • Loss of consortium for the victim's family and loved ones.

They also seek the assessment of punitive damages against Pfizer to punish the company for its conduct.

Because there are so many victims who have been hurt in similar ways, these Xeljanz lawsuits are ripe for consolidation in an MDL, or multidistrict litigation. However, the court system has not yet created one.


  1. FDA Approval Letter for Xeljanz (November 6, 2012).

  2. Press Release, “Pfizer Announces FDA Approval of Xeljanz® (tofacitinib) and Xeljanz® XR for the Treatment of Active Psoriatic Arthritis,” Pfizer, (December 14, 2017).

  3. FDA Approval Letter for Xeljanz to Treat Ulcerative Colitis (May 30, 2018).

  4. See Rahimtoola A, Bergin JD, “Acute pulmonary embolism: an update on diagnosis and management,” Current Problems in Radiology 30(2):61-114 (February 2005).

  5. Barritt DW, Jordan SC, “Anticoagulant Drugs in the Treatment of Pulmonary Embolism,” The Lancet 275(7138):1309-12 (June 18, 1960).

  6. ClinicalTrials.gov Identifier No. NCT02092467, “Safety Study Of Tofacitinib Versus Tumor Necrosis Factor (TNF) Inhibitor In Subjects With Rheumatoid Arthritis.”

  7. Press Release, “Communication of new safety information for XELJANZ (tofacitinib),” Pfizer (February 28, 2019).

  8. Press Release, “Increased risk of pulmonary embolism and mortality in rheumatoid

    arthritis patients receiving 10mg twice daily in a clinical trial,” Pfizer (March 26, 2019).

  9. See note 8.

  10. See note 7.

  11. FDA Drug Safety Communication, “Safety trial finds risk of blood clots in the lungs and death with higher dose of tofacitinib (Xeljanz, Xeljanz XR) in rheumatoid arthritis patients; FDA to investigate,” (February 25, 2019); Allison Prang, "FDA Requires Box Warnings for Pfizer Drug Xeljanz Patients taking 10-milligram dose twice a day could experience a higher risk of blood clots or death," Wall Street Journal (July 26, 2019).

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