Background/Purpose:

In March 2016, the AAO updated antimalarial medication screening recommendations for retinopathy prevention, with a recommended dose of hydroxychloroquine (HCQ) ≤5.0 mg/kg total body weight (TBW) as compared to ≤6.5 mg/kg ideal body weight (IBW) previously. To assess guideline implementation at the two-year mark, we compared HCQ dosing before the March 2016 update and at March 2018. We also assessed whether there was adherence to screening eye exams and evidence of retinal toxicity.

Methods:

We performed a retrospective chart review of patients on HCQ at Albany Medical Center between March 2009 through March 2018. HCQ doses based on TBW and IBW prior to the recommendation updates on March 2016 were compared to TBW-based dosing at March 2018 post-guidelines. We assessed frequency of eye examinations and evidence of retinal toxicity.

Results:

Of 248 charts reviewed, 178 were excluded due to insufficient follow-up or insufficient data for paired analysis between 3/2016 and 3/2018. 70 subjects were analyzed; 64 were female. The mean age was 42.9-years-old (95% CI 39.2-46.6). Mean duration of HCQ therapy at 3/2018 was 62.2 months (95% CI 52.4-71.9). TBW did not change between initiation of HCQ (79.5 kg, 95% CI 74.0-85.2), at 3/2016 (83.0 kg, 95% CI 77.2-88.7), or at 3/2018 (82.9 kg, 95% CI 77.0-88.8) (p=0.64). TBW-based dosage was significantly less at 3/2018 (3.9 mg/kg, 95% CI 3.6-4.2) than TBW-based at 3/2016 (4.3 mg/kg, 95% CI 4.0-4.7) (p<0.03). The TBW-based dosage was significantly less at 3/2018 (3.9 mg/kg, 95% CI 3.6-4.2) than IBW-based dosage at 3/2016 (5.8 mg/kg, 95% CI 5.4-6.2) (p<0.001). At 3/2016, 34 subjects (49%) were dosed at >6.5 mg/kg IBW (mean 7.4 mg/kg, 95% CI 7.1-7.6) and 7 subjects (10%) at >6.5 mg/kg TBW (mean 7.6 mg/kg, 95% CI 7.2-8.1). At 3/2018, 6 subjects (9%) were dosed at >5.5 mg/kg TBW (mean 6.2 mg/kg, 95% CI 5.4-6.9). Comparing the overdosed groups, the number of subjects and the TBW dosage of HCQ at 3/2018 were less than the IBW dosage of HCQ prior to 3/2016 (p<0.001). 34 of 70 (49%) patients had documented retinal exams either annually or biannually. Of the 34 IBW-overdosed at 3/2016, 30 (88%) were appropriately dosed based on TBW by 3/2018. 13 of 34 (38%) and 4 of 7 (57%) overdosed subjects based on IBW and TBW dose at 3/2016, respectfully, did not have eye exams. 4 of 7 (57%) overdosed based on TBW at 3/2018 did not have eye exams. One incidence of retinal toxicity was found and was overdosed (7.5 mg/kg) based on the IBW at 3/2016.

Conclusion:

After the AAO 2016 recommendations, dosing of HCQ decreased based on the change from IBW to TBW. The majority of patients with prior overdosing were re-dosed appropriately by 3/2018.The number of subjects overdosed on HCQ declined at two-year follow-up. Closer retinal exam follow-up is needed to improve screening and prevent toxicity. Overall, the proportion of patients at-risk based on dosage was reduced.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/practices-of-hydroxychloroquine-dosing-based-on-the-american-association-of-ophthalmology-aao-2016-recommendations-a-single-center-experience/