Association of Hydroxychloroquine use and Hemolytic Anemia in Patients With Low Levels of Glucose-6-Phosphate Dehydrogenase

Elucidating the mechanisms and efficacy of antimalarial drugs in systemic lupus erythematosus

INTRODUCTION

Antimalarials (AMs) are old drugs with a wide range of beneficial effects in systemic lupus erythematosus (SLE) beyond the control of activity. The most recent debate is focused on defining the optimal doses to assure the best benefit/risk ratio.

AREAS COVERED

We have reviewed the pharmacological basis underlying the various therapeutic effects of AMs and the beneficial and toxic effects of HCQ, also discussing the role of mepacrine not only as a substitute in cases of maculopathy, but also as a very effective therapy combined with HCQ. We searched PubMed and Embase for articles published in English at any time. We used the terms "hydroxychloroquine" or "mepacrine" or "chloroquine" or "antimalarials", "pharmacokinetics", "efficacy", "remission", "toxicity", "adherence". We reviewed original research articles, large observational studies, systematic reviews, and expert consensus statements. Additionally, studies were identified through the assessment of the reference lists of the evaluated manuscripts.

EXPERT OPINION

We advocate for the widespread use of HCQ at stable doses of 200 mg/d (≤4 mg/kg/d for most patients) and also for the early combination therapy with mepacrine to assure a good control of SLE activity, and also a durable and safe use of these essential drugs for the management of SLE.

The Role of Methemoglobin and Carboxyhemoglobin in COVID-19: A Review

Following the outbreak of a novel coronavirus (SARS-CoV-2) associated with pneumonia in China (Corona Virus Disease 2019, COVID-19) at the end of 2019, the world is currently facing a global pandemic of infections with SARS-CoV-2 and cases of COVID-19. Since severely ill patients often show elevated methemoglobin (MetHb) and carboxyhemoglobin (COHb) concentrations in their blood as a marker of disease severity, we aimed to summarize the currently available published study results (case reports and cross-sectional studies) on MetHb and COHb concentrations in the blood of COVID-19 patients. To this end, a systematic literature research was performed. For the case of MetHb, seven publications were identified (five case reports and two cross-sectional studies), and for the case of COHb, three studies were found (two cross-sectional studies and one case report). The findings reported in the publications show that an increase in MetHb and COHb can happen in COVID-19 patients, especially in critically ill ones, and that MetHb and COHb can increase to dangerously high levels during the course of the disease in some patients. The medications given to the patient and the patient’s glucose-6-phospate dehydrogenase (G6PD) status seem to be important factors determining the severity of the methemoglobinemia and carboxyhemoglobinemia. Therefore, G6PD status should be determined before medications such as hydroxychloroquine are administered. In conclusion, MetHb and COHb can be elevated in COVID-19 patients and should be checked routinely in order to provide adequate medical treatment as well as to avoid misinterpretation of fingertip pulse oximetry readings, which can be inaccurate and unreliable in case of elevated MetHb and COHb levels in the blood.