We investigated the efficacy and safety of hydroxychloroquine for empirical treatment of outpatients with confirmed COVID-19.

In this prospective, single-center study, we enrolled ambulatory outpatients with COVID-19 confirmed by a molecular method who received hydroxychloroquine. The patients were divided into low- and moderate-risk groups based on the Tisdale risk score for drug-associated QT prolongation, and the QT interval was corrected for heart rate using the Bazett formula (QTc). The QTc interval was measured by electrocardiography both pretreatment (QTc1) and 4 h after the administration of hydroxychloroquine (QTc2). The difference between the QTc1 and QTc2 intervals was defined as the ΔQTc. The QTc1 and QTc2 intervals and ΔQTc values were compared between the two risk groups.

The median and interquartile range (IQR) age of the patients was 47.0 (36.2–62) years, and there were 78 men and 74 women. The median (IQR) QTc1 interval lengthened from 425.0 (407.2–425.0) to 430.0 (QTc2; 412.0–443.0) milliseconds (ms). However, this was not considered an increased risk of ventricular tachycardia associated with a prolonged QTc interval requiring drug discontinuation, because none of the patients had a ΔQTc of >60 ms or a QTc2 of >500 ms. Moreover, the median (quartiles; minimum-maximum) ΔQTc value was higher in patients in the moderate-risk group than those in the low-risk group (10.0 [−4.0–18.0; −75.0–51.0] vs. 7.0 [−10.5–23.5; −53.0–59.0 ms]) (p = 0.996). Clinical improvement was noted in 91.4% of the patients, the exceptions being 13 patients who presented with non-serious adverse drug reactions or who had severe COVID-19 and were hospitalized. Adverse effects related to hydroxychloroquine were non-serious and occurred in 52.8% (n = 80) of the patients.

Our findings show that hydroxychloroquine is safe for COVID-19 and not associated with a risk of ventricular arrhythmia due to drug-induced QTc interval prolongation. Additionally, hydroxychloroquine was well tolerated, and there were no drug-related non-serious adverse events leading to treatment discontinuation in the majority of patients who were stable and did not require hospitalization.