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Sulfasalasine and Covid-19 infection

Sulfasalasine, a disease-modifying antirheumatic drug (DMARD), has a well-established role in the treatment of patients with chronic inflammatory diseases, such a rheumatoid arthritis, inflammatory bowel disease and psoriatic arthritis.  It is often used in patients who are unable to tolerate methotrexate. Sulfasalasine has anti-inflammatory, immunosuppressive,  and antibiotic actions, though the precise mechanism of action is unknown. 

Several recently published studies have shown that taking sulfasalasine may significantly increase the risk of severe Covid-19 infection and death1.  Patients taking sulfasalazine were more likely to be hospitalized, be sent to an intensive care unit, or die as a result of complications from the virus. This association has become known in several large patient registries, including the COVID-19 Global Rheumatology Alliance2, the SECURE-IBD registry3, and an analysis of data from Swedish patients with rheumatoid arthritis4.

Exactly why sulfasalasine should increase the risk of Covid-19 infection, cannot be explained by any of its known mechanisms of action. However, recent findings suggest that the association of sulfasalazine with poor COVID-19 outcomes, could be related to a previously unappreciated ability of the drug to inhibit a special protein called type I interferon (IFN-1).  This is important, because type I interferons have long been recognized as playing an essential role in the body’s protection against viral infections.  Clearly if sulfasalasine is inhibiting the action of interferons, it could explain why patients taking the drug are much more vulnerable to serious Covid-19 infections.

Clearly more research is needed, but what does this mean for you if you are currently taking sulfasalasine?


  • Do not stop taking your medicine; sulfasalasine is an effective drug in many people with inflammatory conditions (including psoriatic arthritis) and discontinuing it abruptly may have unwanted effects.
  • Do talk to your doctor and take advice as to whether sulfasalazine is right for you, and – very importantly…
  • Do make sure you are fully up to date with your Covid-19 vaccinations – including boosters.


  1. Konig MF,  Grzes KM, et al.  Sulfasalasine: a risk factor for severe COVID-19?
  2. Lancet Rheumatol. 2022 Jun; 4(6): e388–e389.  Published online 2022 Mar 15. 
  3. Strangfeld A, Schafer M, Gianfrancesco MA et al. Factors associated with COVID-19- related death in people with rheumatic diseases: results from the COVID-19 Global Rheumatology Alliance physician-reported registry. Ann Rheum Dis. 2021; 80: 930-942
  4. Brenner EJ, Ungaro RC, Gearry RB et al. Corticosteroids, but not TNF antagonists, are associated with adverse COVID-19 outcomes in patients with inflammatory bowel diseases: results from an international registry. Gastroenterology. 2020; 159 (91.e3): 481
  5. Bower H, Frisell T, Di Giuseppe D et al. Impact of the COVID-19 pandemic on morbidity and mortality in patients with inflammatory joint diseases and in the general population: a nationwide Swedish cohort study. Ann Rheum Dis. 2021; 80: 1086-1093
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