Another key to minimizing retinopathy risk in patients on hydroxychloroquine is to pay careful attention to how long they’ve been on the drug. As the years go by in patients being treated for cutaneous lupus or other dermatologic disorders where decades-long therapy is often a mainstay, it’s important to check with patients and make sure they’re getting annual ophthalmologic screening for irreversible retinal toxicity by both threshold visual fields and spectral domain optical coherence tomography. In the large, practice-changing retrospective study, patients on hydroxychloroquine at 4.0-5.0 mg/kg daily had a prevalence of retinopathy of less than 2% during the first 10 years of therapy, but the rate shot up to nearly 20% after 20 years of use, Dr. Stratman observed.
He highlighted as helpful an updated review of the use of hydroxychloroquine in dermatology recently published by Anthony P. Fernandez, MD, PhD, of the department of dermatology at the Cleveland Clinic (J Am Acad Dermatol. 2017 Jun;76[6]:1176-82).
Dr. Fernandez recommends following the AAO guidance to dose the drug at 5.0 mg/kg or less of actual body weight in thin or normal-weight patients; however, he departed from the ophthalmologists with regard to treatment of obese patients. Because dosing based on actual weight could potentially lead to relative overdosing in obese patients, in that growing population he recommends calculating the dose based upon 5.0 mg/kg of actual body weight, as well as the dose based on 6.5 mg/kg of ideal body weight, then prescribing the lower of the two, up to a maximum of 400 mg/day.
“The current recommendation is really about not overdosing thin patients. Basically, dosing is not so difficult for obese people because if you weigh more than 175 pounds, you’re going to get 400 mg/day,” Dr. Stratman explained.
That 400 mg/day ceiling is not cast in stone, he continued. The guideline recommends that, if a patient is a nonresponder to several months of hydroxychloroquine at 400 mg/day, it’s worthwhile to order a drug blood level. If it’s not above the efficacy threshold of more than 750 ng/mL, it’s appropriate to titrate up.