Retina chloroquine

The eye may be a target organ as a result of its external position in the organism and direct exposure, but also from systemic exposure. Thus, the various components of the eye may be specifically damaged. The presence of pigments in the eye such as melanin has been suggested as the cause of chloroquine toxicity to the retina. 

Adverse Effects. The most serious problem associated with chloroquine is the possibility of toxicity to the retina and subsequent visual disturbances. This issue is usually insignificant, however, when this drug is used for short periods in relatively low doses (see Chapter 16). Other relatively mild side effects may occur, including gastrointestinal distress (nausea, vomiting, stomach cramps, diarrhea), behavior and mood changes (irritability, confusion, nervousness, depression), and skin disorders (rashes, itching, discoloration). 

There have been occasional reports of retinopathy resembling that seen with chloroquine (SEDA-11, 593) (2). However, as a rule mepacrine is non-toxic to the retina (SEDA-14, 241). 

The presence of pigments in the eye such as melanin has been suggested as the cause of chloroquine toxicity to the retina. 

Quinacrine, which is tricyclic and highly lipophilic, will easily penetrate cell membranes but hardly diffuse through the hydrophilic vitreous cavity. It also forms a stable complex with melanin and will therefore be retained in the RPE. Quinacrine must be considered a potent photosensitizer in the retina due to the absorption maximum of this drug in the visible region of the spectrum (Table 10.1). The more hydrophilic compounds chloroquine and hydroxychloroquine will more easily be transported to the lens. They are known to accumulate in the eye and induce toxic reactions. Primaquine is not likely to be distributed to the eye to any extent due to low distribution volume and fast elimination. 

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