Initial trough levels of ≥20 mg/L but not ≥15 mg/L were associated with early-onset VCM-associated nephrotoxicity in critically ill patients. Future prospective studies are needed to examine outcomes in critically ill patients achieving initial VCM trough levels of 15-20 mg/L.

What is known and objective: Favipiravir is a promising treatment candidate for managing coronavirus disease 2019 . Warfarin has many drug interactions, but no interactions with favipiravir have been reported. Case summary: Our patient was taking warfarin for deep vein thrombosis. The international normalized ratio (INR) was stable (1.65 to 2.0); however, it increased to 4.63 after administering favipiravir. The patient had no other factors justifying this change. What is new and conclusion: Favipiravir and warfarin might have previously unidentified drug interactions that elevated the INR. Therefore, INR must be closely monitored when they are concomitantly administered in COVID-19 patients. K E Y W O R D S coronavirus disease of 2019 (COVID-19), cytochrome P-450 (CYP), drug-drug interactions (DDIs), favipiravir, international normalized ratio (INR), warfarin How to cite this article: Sekimoto M, Imai T, Hidaka S, et al.

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Objective To examine the effect of angiotensin II receptor blocker (ARB) treatment on serum potassium level and hyperkalaemia risk in a clinical setting with inpatients and outpatients using calcium channel blockers (CCBs) as a reference standard. Methods The increased risk of hyperkalaemia associated with ARB treatment is known, however only a few studies have used an active comparator to examine this risk. In this retrospective study at a 320-bed general hospital in Japan, the hospital information system was used to identify patients with at least one prescription for an ARB (819 patients) or a CCB (1015 patients) who were naive to these drugs before study initiation. Serum potassium levels before and after ARB treatment were compared. Additionally, the unadjusted and adjusted hazard ratios for the risk of hyperkalaemia in the ARB and CCB users were estimated. Results The serum potassium level was higher in patients receiving ARB treatment (0.05 mEq/L, p=0.02) compared with those on CCB treatment. However, there was no significant association between ARB use and hyperkalaemia (adjusted HR 0.91, 95% CI 0.42 to 1.99, p=0.82). ConclusionThe increase in serum potassium level after ARB initiation makes it necessary to monitor serum potassium levels continuously during ARB treatment; however, the risk of hyperkalaemia appeared to be similar for ARB and CCB treatments.