LAUSR

BACKGROUND Nafamostat mesylate (NM) may prove to be one of the key drugs effective against coronavirus disease 2019 (COVID-19) because of its anti-viral properties and the potential to manage coagulopathy. However, NM tends to increase serum potassium levels. CASE SUMMARY We observed hyperkalemia immediately after NM administration (200 mg/d) in four consecutive patients who were admitted to the Kanazawa University Hospital with severe COVID-19 pneumonia. Urinary potassium excretion decreased after NM administration in three patients who underwent urinalysis. CONCLUSION NM is likely to produce hyperkalemia in patients with COVID-19. Therefore, it is necessary to monitor serum potassium values closely after NM initiation in COVID-19 patients who need respiratory support.