(Hydroxy)-chloroquine retinal toxicity: two case reports and safety guidelines.

Retinal toxicity as a result of antimalarial therapy has been reported for many years. Retinopathy may be divided into reversible premaculopathy and irreversible true retinopathy. Risk factors for the development of toxicity are daily dosage related to body weight, total drug dosage and the specific drug used. The daily dosage of chloroquine should not exceed 4 mg/kg lean body weight a day. Exceeding the total dosage of 300 g increases the risk. The daily dosage of hydroxychloroquine should not exceed 6.5 mg/kg lean body weight a day with increased risk when the duration of treatment exceeds 8 years (1330 g for a patient of 70 kg). Regular dilated fundus examination, visual field testing using Amsler grid test and automated central 10-2 perimetry (to a red test object) is advised to detect reversible premaculopathy. Hydroxychloroquine toxicity due to excessive cumulative dosage is discussed in case 1. Chloroquine toxicity due to excessive daily dosage is discussed in case 2.