Check the medication

Ophthalmologists who care for patients being treated with hydroxychloroquine (Plaquenil) should remember to check the patient’s medication dose in addition to checking their eyes, said researchers from Bronx-Lebanon Hospital Center, Bronx, New York, at the 2015 annual meeting of the Association for Research in Vision and Ophthalmology in Denver, USA.

They reached this conclusion after examining records of patients seen in the outpatient service between December 2008 and May 2014. The researchers identified 643 patients who had been prescribed hydroxychloroquine. Daily doses for each patient were compared to the American Academy of Ophthalmology recommendations that state a hydroxychloroquine dose of 400mg/day is acceptable, except for persons of short stature who should receive <6.5mg/kg ideal body weight/day (Ophthalmology. 2011;118:415–422).

The review found 86 per cent of patients were receiving a daily dose of 400mg. However, calculations of weight-based doses showed 70 per cent of patients were being treated with a daily dose >6.5mg/kg of ideal body weight, and the dose in almost one-fourth of those patients (16 per cent overall) exceeded the 6.5mg/kg threshold by more than 30 per cent.

“Tall and average height people are easily within the safe range of 6.5mg/kg ideal body weight/day. However, one has to be more careful in short stature people because the standard 400mg/day dose may be too much,” said Jonathan Levine MD, a retina specialist.

“When in doubt, pull out the calculator, and remember that unlike other medications for which dosing is based on actual body weight, hydroxychloroquine is dosed according to ideal body weight,” he advised.

DOSING PRESCRIPTION

Jing Grace Wang DO, PhD noted that the dosing decision for each patient is ultimately up to the judgment of the prescribing physician, taking into account the risks and benefits of different dosing levels.

“However, if it is determined that a higher dose is needed, patients need to be educated about the risk of macular toxicity and the importance of ophthalmologic follow-up,” she said.

Dr Wang acknowledged that dosing flexibility is limited with hydroxychloroquine since the medication is only available as a 200mg tablet. When 400mg/day is too much, patients can be prescribed 300mg/day, which requires splitting a tablet, or they can take 400mg/day and 200mg/day on alternate days. “Success with those more complex regimens requires good patient education,” said Dr Wang.

She also noted that use of the electronic medical record system at the Bronx-Lebanon Hospital has facilitated effective communication about retinopathy status and dosing concerns between the department of ophthalmology and physicians prescribing hydroxychloroquine.

Jonathan Levine: jlevine1@bronxleb.org

Jing Grace Wang: jinggracewang@gmail.com