Potassium iodide sufficient in continuing treatment of erythema nodosum

Potassium iodide offers a rapid response in the treatment of erythema nodosum and may be an adequate option for patients who do not respond to the standard of care, according to a presentation at the Interdisciplinary Autoimmune Summit.

“Erythema nodosum can be idiopathic but is very frequently associated with an underlying disease. Patients usually either present with a history of triggers but not infrequently do require a workup to confirm what the trigger might be,” Daniela Kroshinsky, MD, MPH, associate professor of dermatology at Harvard Medical School, said. “Treatment first and foremost relies on identifying the trigger. ... If that is insufficient for improving this scenario or relieving pain, we start to think about things like potassium iodide.”

While erythema nodosum usually resolves by itself within 2 to 6 weeks, initial patient evaluation of medication history and travel history along with a review of respiratory, gastrointestinal and constitutional systems helps identify and treat the underlying cause of inflammation. Recommended lab testing includes CBC, ESR, CRP, rapid throat culture and ASO titer that is repeated in 2 to 4 weeks. First-line care includes elevation, rest and anti-inflammatory medications such as salicylates and NSAIDs, Kroshinsky said.

Further treatment with potassium iodide 300 mg to 1,500 mg per day offers a fast onset that is well tolerated without immunosuppressing patients.

“The acute possible side effects include nausea, bitterness and excessive salivation, rarely urticaria, angioedema or small vessel vasculitis, which I personally have not seen in patients, and I have prescribed quite a bit of potassium iodide over the years,” Kroshinsky said. “Most patients just require a 2-week to 4-week course really just to get things under control.”