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Patients with psoriatic arthritis (PsA) report more side effects from newly initiated methotrexate (MTX) than do patients with rheumatoid arthritis (RA). In a study by Alexis Ogdie, MD, and colleagues, published in , PsA patients initiated on methotrexate had greater self-reported gastrointestinal (GI) symptoms, paresthesias, muscle weakness, depression, and tinnitus. Patients with PsA were also more likely to have higher body mass index (BMI), fibromyalgia, and depression than RA patients.

This was an observational study using self-reported data from 2000-2019. There were fewer patients with PsA than patients with RA. Researchers also evaluated side effects from newly initiated tumor necrosis inhibitors (TNFi). Of note, patients on both MTX and TNFi were included in this study. Side effects were evaluated within the first 12 months of the newly initiated drug. The researchers did not name the specific brand of TNFi nor how many patients were receiving subcutaneous MTX.

Side effects from MTX were 1.8 fold higher in patients with PsA compared to RA once confounders (age, gender, BMI) were adjusted. Among patients newly initiated on a TNFi, effects were similar between both groups.

As we know, patient-reported side effects can differ from physician-reported side effects. This study is important in practice as patient-reported side effects can lead to noncompliance and poor outcomes. It may also make it difficult for patients to trust future treatment options. Variables associated with higher reporting included depression, GI symptoms, anxiety, subcutaneous administration, having some college education, higher patient activity scale, and a higher score on the health assessment questionnaire (HAQ-II).

Understanding treatment burden from a patient's point of view allows physicians to provide accurate warnings and side effects profiles, some of which may be more common in certain groups of patients -- ie, those with PsA or RA; the elderly; females; and those with higher BMI, depression, underlying GI disorders, and fibromyalgia. Difficulties with such studies include patient-related bias and lack of causation; therefore, results should be interpreted with caution.

Understanding why PsA patients may have more comorbid conditions and a higher side effect profile will be key to identifying successful treatment and management regimens. The potential role of higher BMI and MTX side effects is also an important takeaway.

Sneha Patel, MD, practices rheumatology in Ft. Worth, Texas.

Read the study here and a Q&A with a study co-author here.