Drug Interactions between chloroquine and deferoxamine

GENERALLY AVOID: Hydroxychloroquine (HCQ) and chloroquine (CQ) can cause dose-related retinal toxicity. The risk of retinal toxicity from HCQ or CQ increases with concurrent use of drugs known to induce retinal toxicity, higher doses (greater than or equal to 5 mg/kg of actual body weight for HCQ and 2.3 mg/kg of actual body weight for chloroquine), treatment duration >5 years, low body weight, advanced age, and concomitant retinal, renal, or hepatic disease. The precise mechanism of retinal toxicity is unclear, but it is thought to be associated with high concentrations of 4-aminoquinoline (4-AQ) from HCQ and CQ in the ocular tissue, which binds to melanin in the retinal pigment epithelium (RPE), ultimately leading to inner and outer retinal damage. This damage disrupts crucial steps in the visual cycle, resulting in lipofuscin accumulation and photoreceptor degradation. Retinal toxicity is more commonly associated with CQ than with HCQ and can result in the development of circular defects (bull's eye maculopathy) and diametric defects of the retina. In a retrospective case-control study evaluating 2361 patients within an integrated health organization who had used HCQ continuously for at least 5 years, visual field (VF) testing or spectral-domain optical coherence tomography (SD-OCT) were used to identify the presence of retinal toxicity. The overall prevalence of retinopathy was 7.5% and increased significantly with higher daily doses (>5.0 mg/kg) and long-term use (>10 years). Additionally, concomitant use of tamoxifen with HCQ increased the risk of retinal toxicity by approximately 5-fold.

MANAGEMENT: Coadministration of hydroxychloroquine (HCQ) or chloroquine (CQ) with other drugs that can induce retinal toxicity should generally be avoided. If coadministration is required, ophthalmological examinations including best corrected distance visual acuity (BCVA), automated threshold VF and SD-OCT tests should be started one year after therapy is initiated and repeated annually. In addition, maintaining HCQ doses of <5 mg/kg of actual body weight and CQ doses of <2.3 mg/kg of actual body weight are recommended to reduce retinal toxicity risk. Individual product labeling and local guidelines should be consulted for additional guidance.