A substantial number of rheumatology patients are receiving excess starting and maintenance doses of hydroxychloroquine despite the existence of dosing guidelines, a group of ophthalmologists has reported.
The report raises some concerns because hydroxychloroquine has well-established ocular side effects and toxicities that makes screening by a ophthalmologist necessary for all patients on long-term therapy.
Rebekah A. Braslow, MD, and her colleagues in the division of ophthalmology at NorthShore University HealthSystem in Illinois conducted a retrospective review of the records of 554 rheumatology patients who were prescribed hydroxychloroquine during 2009-2016 and seen by a NorthShore ophthalmologist. They found that about half of the patients were on excess initial doses of the disease-modifying antirheumatic drug, according to retinal toxicity guidelines published by the American Academy of Ophthalmology (AAO) in 2011. There was no difference in the percentage of patients on an excess starting dose before the 2011 guidelines were published (54% of 92 patients) or after (49% of 462). The maintenance dose 1 year after beginning treatment was the same as the starting dose in 84% of patients, with reductions in 7% and increases in 9% ( Ophthalmology. 2017 Jan 30. doi: 10.1016/j.ophtha.2016.12.021 ).
The AAO revised the guidelines in 2016 to define excess doses of hydroxychloroquine as greater than 5.0 mg/kg of actual body weight ( Ophthalmology. 2016;123:1386-94 ). Based on these new guidelines, the investigators found that 56% of 527 patients who were currently receiving hydroxychloroquine were taking excess doses, and 43% of the 527 patients were still receiving doses that are more than 50 mg in excess of the calculated target dose that is recommended by the guidelines.
“The published ophthalmology screening guidelines have had no appreciable impact on clinical practice, highlighting a persistent deficiency in patient care and a significant medico-legal risk,” they concluded.
“Our findings are particularly concerning given that choosing a proper starting dose is the single safest, simplest, and most cost-effective measure available,” they wrote.
According to the authors, there were several reasons for the widespread inaccurate dosing. Firstly, the guidelines were published in ophthalmology literature and were therefore unlikely to be seen by rheumatologists. Secondly, the formulation of the drug, currently available only in 200-mg tablet form, made it difficult to adjust doses according to a patient’s weight.
This particular issue could be addressed if the drug manufacturers expanded formulation options, or by alternating daily dosing regimens or involving compound pharmacies, they suggested.
System-wide education and prompts via electronic medical records would also go some way toward ensuring that patients are prescribed the correct dose, they added.
The study was supported by intramural research funds within the division of ophthalmology in NorthShore University Health System.