July 23, 2018
2 min read

Nearly half of female hydroxychloroquine users in UK excess-dosed

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Approximately 47% of female patients in the United Kingdom who are prescribed hydroxychloroquine are given excess doses, based on ideal-body-weight dosing, according to findings published in Arthritis Research & Therapy.

When using actual-body-weight dosing, the researchers found that 38% are excess-dosed.

“Previously, the 2009 Royal College of Ophthalmologists (RCO) and 2011 American Academy of Ophthalmology (AAO) guidelines [on hydroxychloroquine] each recommended a maximum safe dose of 6.5 mg/kg/day of ideal body weight (IBW) — up to a maximum of 400 mg daily — to minimize the risk of retinopathy,” April M. Jorge, MD, of Massachusetts General Hospital, and colleagues wrote. “However, in 2016, the AAO updated their maximum daily dose recommendation to 5 mg/kg/day actual body weight (ABW), based largely on a retrospective study based in Kaiser Permanente Northern California.”

Approximately 47% of female patients in the United Kingdom who are prescribed hydroxychloroquine are given excess doses, based on ideal-body-weight dosing, according to findings.
Source: Shutterstock

Jorge and colleagues also wrote that, despite previous recommendations, “there may have been less concern about [hydroxychloroquine] retinopathy in the United Kingdom than in the United States, as the RCO had not recommended routine hydroxychloroquine retinopathy screening prior to 2017.

“To that end, to what extent recent [hydroxychloroquine] prescriptions would exceed dosing recommended by ophthalmology guidelines remain unknown,” they wrote.

To evaluate recent prescription trends and determine the predictors of potential excess dosing in the United Kingdom, the researchers used data from the Health Improvement Network to analyze hydroxychloroquine prescribing patterns compared with dosing guidelines over a period of 10 years. The Health Improvement Network is an electronic medical record database representing 6.2% of the U.K population, or about 11 million patients. In all, the researchers identified 20,933 new hydroxychloroquine users between 2007 and 2016. Of those, 78% were female.

The researchers defined excess dosing as exceeding 6.5 mg/kg of IBW and 5 mg/kg of ABW, and determined their predictors using multivariable logistic regression analyses.

According to the researchers, the proportions of initial excess dosing during the study period fell to 36%, from 40%, based on IBW, and to 30%, from 38%, using ABW. Among those patients, 47% of women received excess doses of hydroxychloroquine (OR = 12.52; 95% CI, 10.99-14.26) based on IBW, and 38% (OR = 1.98; 95% CI, 1.81-2.15) based on ABW. Examining BMI, the researchers found that 37% of normal-weight patients, and 44% of those who were obese, received excess doses based on IBW (P < .01). However, using ABW, those figures changed to 53% of normal-weight patients and 10% of those who were obese (P < .01).


“Over half of normal BMI individuals were excess-dosed per the latest guidelines; however, BMI had a noticeably opposite impact on the risk of excess dosing between the prior and latest weight-based guidelines,” Jorge and colleagues wrote. “This implies the potential need to reduce dosing in many patients but also calls for further research to establish unifying, evidence-based safe-dosing strategies, balancing retinopathy risk and treatment efficacy.” – by Jason Laday

Disclosure: Jorge reports no relevant financial disclosures. Please see the study for all other authors’ relevant financial disclosures.