Glucose-6-phosphate dehydrogenase deficiency (G6PD) is linked to hemolytic anemia with certain medications and is the most common enzyme deficiency worldwide. Although the American College of Rheumatology does not recommend routine testing for G6PD prior to initiation of hydroxychloroquine (HCQ), the package insert for HCQ does recommend careful use in patients with G6PD deficiency.

We identified eligible subjects seen at our tertiary care, urban medical center between 1997 and 2018. Case records were analyzed for G6PD deficiency, HCQ use, length of exposure to HCQ, demographic characteristics, and laboratory evidence of hemolysis.

We found 5264 patients who were prescribed HCQ, of which 49.5% (2605 patients) were screened for G6PD deficiency. Of the screened patients, 36 were found to be G6PD-deficient. Of the G6PD-deficient patients, 18 were exposed to HCQ. No evidence of hemolysis was found in these exposed patients.

Despite more than 500 months of cumulative exposure time to HCQ, there were no cases of hemolysis. These findings are in line with recently published data and suggest that this interaction is not associated with clinically significant hemolysis in our population of mainly African American and Hispanic patients. Limitations to our study are potential bias due to case review design and lack of prior assessment of episodes of hemolysis before HCQ exposure. A high proportion of our patients were Hispanic, suggesting no increase of adverse events in this subgroup. A larger longitudinal trial would be needed to definitively answer the question of the safety of HCQ in G6PD-deficient patients.