Risk for adverse events from trimethoprim-sulfamethoxazole higher in patients with lupus
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Patients with systemic lupus erythematosus, especially those who are positive for anti-Sm antibodies, are at greater risk for adverse events associated with trimethoprim-sulfamethoxazole, according to data presented at the ACR Convergence 2020 virtual meeting.
Though the researchers suggest close monitoring in these patients, they emphasized that providers should not hesitate to prescribe trimethoprim-sulfamethoxazole (TMP-SMX) to patients who need it.
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“This medication sometimes causes various side effects, and lupus patients tend to be at high risk for adverse drug reactions, from my experience,” study co-author Shinji Izuka, MD, a rheumatologist and researcher at the National Centre for Global Health and Medicine in Tokyo, said during a press conference. “This is sometimes confusing as to how to treat lupus patients mostly because adverse drug reactions, such as cytopenia or skin rash, are also among the manifestations of flare in lupus.”
Previous studies have shown an increased risk for adverse events associated with TMP-SMX in patients with SLE, which prompted Izuka and colleagues to aim to confirm this association and determine risk factors.
Using in-patient data from their hospital, the researchers retrospectively reviewed records for patients with connective tissue disease who were administered prophylactic TMP-SMX for pneumocystis pneumonia between January 2009 and April 2020. The prevalence of adverse drug events was compared between patients with SLE and those with other connective tissue diseases; however, patients with HIV and those who did not experience adverse drug events but received TMP-SMX within 1 month were excluded.
A total of 427 patients with connective tissue disease were included, specifically: SLE (n = 164), polymyositis or dermatomyositis (n = 83), Sjögren syndrome (n = 25), systemic sclerosis (n = 22), mixed connective tissue disease (n = 11), eosinophilic granulomatosis with polyangiitis (n = 17), granulomatosis with polyangiitis (n = 22), microscopic polyangiitis (n = 46), polyarteritis nodosa (n = 10), Takayasu arteritis (n = 7) and giant cell arteritis (n = 20).
Adverse drug events occurred in 40 patients and included thrombocytopenia (n = 10), skin rash (n = 9), liver function test abnormality (n = 7), fever (n = 7), and others (n = 12). Among patients with SLE, the prevalence of adverse drug events was 13.4% compared with 6.9% in the control group, with an OR of 2.12 (95% CI, 1.05-4.35). For patients with all other connective tissue diseases, the OR for adverse drug events was not significantly different, according to the researchers.
Risk factors for adverse drug events among patients with lupus were determined using univariate and multivariate analyses. In the univariate analysis, these included: anti-Sm antibody positivity (OR = 5.44; 95% CI, 1.93-16.06); anti-RNP antibody (OR = 3.19; 95% CI, 1.11-10.02); and anti-Ro/SS-A antibody (OR = 2.87; 95% CI, 1.06-7.77). Whereas only anti-Sm antibody was significantly associated with risk in the multivariate analysis (OR = 3.34; 95% CI, 1.10-11.10).
“When we administer this medicine to patients, especially patients with anti-Sm antibody, we should monitor them carefully about the adverse events,” Izuka said. “Or, if we do start TMP-SMX in those patients, we can consider ... starting from a very low dose and then increasing it gradually, or administering another agent.”
“While we should be aware of the side effects [of TMP-SMX], preventing pneumocystis pneumonia in high-risk patients is also important because it can be fatal,” Izuka added. “This study may help to anticipate and reduce the adverse drug reactions to TMP-SMX for lupus patients, but the mechanisms remain unclear ... and may differ among patients. Further studies are needed.”
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Izuka S. Abstract #1830. Presented at: ACR Convergence 2020; November 5-9, 2020 (virtual meeting).
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