In patients with SLE do you have concerns about using trimethoprim-sulfamethoxazole (Bactrim) because of a potential risk of lupus flare?

I agree with Dr. @Dr. First Last . I have had too many SLE patients over the years show up in my office with a severe flare from TMP/SMX. We have too many alternative antibiotics these days, including for PJP prophylaxis, so sulfonamide antibiotics should be avoided in SLE patients.

The typical scenario is the patient who goes to the ER or Urgent care with a UTI.

I ask patients to carry with them at all times an updated medication list that includes their drug intolerances and to always have "sulfa antibiotics" in that list. That way, when they are sick in the ER and can't think straight, they can just hand their list to the healthcare providers and protect themselves.

I have had two patients hospitalized with lupus flares after being placed on TMP/SMX by ER physicians, and two others who had diffuse skin eruptions. The med residents who saw the flares and cared for the patients in the hospitals told me how impressed they were with the flares.

The other important thing to consider is whether your patient with SLE really needs PJP prophylaxis. I have seen multiple patients admitted to the hospital with dapsone-induced methemoglobinemia or milder adverse reactions to TMP/SMX. Studies have demonstrated low rates of PJP in SLE, even in patients on high doses of steroids and immunosuppressants like cyclophosphamide or mycophenolate (Schmajuk et al., PMID 30449650, Boone et al., PMID 36279805).

You can also consider checking a CD4 count to risk stratify which subsets of patients with SLE really need PJP prophylaxis (CD4 <300 or ALC <500).

The data regarding this is decades old that Bactrim can lead to a lupus flare. No definitive studies were done and we have all had patients that Bactrim was the best antibiotic choice for them and they did not flare. Perhaps enhancing sun sensitivity may be part of the story. If there is an alternative antibiotic, I will use that to avoid the possible reaction. There are clearly patients that have flared post Bactrim but lupus patients do flare so was it the cause or not remains unanswered and a choice the physician and patient can make with education and discussion.

Yes, I have some concern, mainly because patients with SLE appear to have a higher rate of adverse reactions to TMP-SMX, particularly rash and cytopenias, and these reactions can sometimes mimic or coincide with a lupus flare. However, I do not consider SLE itself a contraindication to Bactrim. If there is a clear indication, particularly PJP prophylaxis, I will still use it with appropriate counseling and monitoring, unless there is a prior significant sulfonamide reaction.

E.g A lupus patient in whom I would consider PJP prophylaxis would be someone at higher infectious risk based on the overall immunosuppressive burden, particularly prolonged moderate- to high-dose glucocorticoids combined with another immunosuppressant such as cyclophos...