Antimalarial retinal complications occurred in about 5% of patients with systemic lupus erythematosus (SLE) exposed to hydroxychloroquine or chloroquine during an average of nearly 13 years of follow-up, without any cases of retinal toxicity occurring within the first 5 years of use, according to findings from a case-control study.
The rate of retinal complications observed in the study is slightly lower or within the range reported in other studies of antimalarial use by patients with SLE, first author Elvis-Raymond Mukwikwi of the University of Montreal and coauthors from McGill University, Montreal, reported in the.
Hydroxychloroquine (HCQ) and chloroquine (CQ) are commonly used to treat SLE and rheumatoid arthritis, and they are being investigated for use in diabetes, cancer, and cardiovascular disease. However, in rare cases, the drugs can lead to irreversible retinopathy.
To better understand the factors associated with retinopathy, the researchers analyzed data from 326 records obtained from the McGill University Health Center Lupus Clinic Registry. A total of 18 patients (5.5%) had confirmed retinal toxicity, and the investigators matched each of these patients to 3 control patients with SLE and exposure to HCQ/CQ who did not develop retinopathy and had the same duration of SLE and age at SLE diagnosis.
The minimum number of years of HCQ/CQ exposure before retinopathy developed was 8 years, and the maximum number was 33 years. Overall, 17 retinopathy cases had exposure to HCQ, and 12 of those cases (71%) received average doses higher than current recommendations. Eight patients were exposed to average daily doses of HCQ higher than 5 mg/kg and four to average daily doses of CQ above 2.3 mg/kg. Exposure to an average dose higher than currently recommended occurred in 49% of controls. The exposure to doses higher than current recommendations was “not surprising given that these were issued in 2016 and most of our patients had been taking HCQ for longer than this,” the authors wrote.
High-dose exposure was common, with 83% of controls and all retinopathy cases having been exposed to HCQ/CQ doses above recommendations, as determined during at least one annual assessment.
Among patients with retinopathy, exposure to CQ was three times more frequent than it was for those without the condition (39% vs. 13%; 95% confidence interval, 1.8%-52%), although all of the patients exposed to CQ also were exposed to long periods of HCQ, making it impossible to determine retinopathy risk to CQ exposure alone.
The researchers also found gaps in monitoring. In the 5 years before discontinuation of medication, 53% of cases had missed one or more annual ophthalmologic assessments to screen for retinal damage, compared with 75% of controls.
Concomitant renal damage, believed to be a risk factor for retinal toxicity, occurred more often in the retinopathy group, though the difference failed to meet statistical significance (23% versus 15%). Patients with retinopathy were less likely to be Caucasian (61% versus 74%), but this also did not reach statistical significance.
The authors did not disclose information on funding or conflicts of interest.
SOURCE: Mukwikwi ER et al. J Rheumatol. 2019 Sep 1.