How is chloroquine and hydroxychloroquine different?

Chloroquine (CQ) is used to prevent and treat malaria and amebiasis,[1] while hydroxychloroquine (HCQ), a less toxic metabolite of chloroquine, is used to treat rheumatic diseases such as systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), juvenile idiopathic arthritis (JIA) and Sjogren's syndrome.[2] Both medications can cause corneal deposits, posterior subcapsular lens opacity, ciliary body dysfunction, and most important, irregularity in the macular pigmentation in the early phase, a ring of macular pigment dropout in the advanced stage, and peripheral bone spicule formation, vascular attenuation, and optic disc pallor in the end-stage. Ocular symptoms of retinopathy include blurred and partial loss of central vision, side vision and in the later stage, night vision.  Symptoms of corneal deposits include haloes and glare.  Clinical research has resulted in precise screening protocols and safe dosing guidelines to prevent ocular toxicity and detect retinal damage at an early stage.

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