Screening for Plaquenil Toxicity

Karen had seen her rheumatologist for many years about her arthritis. At this visit she told her physician that the pains were worse than ever. The doctor prescribed a different medication called plaquenil (generic name hydroxychloroquine) and recommended that she see the retina doctor in the next few weeks because the medication could affect her eyes. At the retina center, Karen had her vision checked and had a thorough exam including dilation of her pupils. Her color vision was checked and she was shown how to perform an Amsler grid test which involved looking at a graph paper with one eye at a time with her reading glasses on.

The retinologist explained that chloroquine was first used to treat malaria but has since been found to be effective in treatment of rheumatoid arthritis and other inflammatory diseases. Retinal toxicity is common at high doses. A closely related drug, hydrochloroquine was found to be considerably less toxic but just as effective. Consequently, chloroquine is rarely used for inflammatory diseases in the United States but is still used outside of the USA. It is used for prophylaxis and treatment of malaria. Both drugs accumulate in the pigmented tissues such as the retinal pigment epithelium and can cause a Bull’s eye retinopathy so named because of its target-like appearance. This is usually found on a special dye test called fluorescein angiography. Dye is injected into the vein in the arm and photos are taken with a retinal camera. Other testing includes visual field testing where lights are flashed at different locations in the patient’s visual field and the patient presses a button whenever the light is seen.

The frequency of retinopathy is less than 5% when dosages of less than 6.5 mg/kg per day of hydroxychloroquine are used. That is usually less than 400 mg/day. The eye doctor is consulted for baseline testing, usually within first 6 months of starting drug. The recommended follow up is 6 months to 1 year. A recent survey of retinologists and rheumatologists found that the majority were doing 6 months follow up. Between follow up appointments, weekly Amsler grid testing at home is recommended.

Risk factors for retinopathy include daily dose greater than 6.5 mg/kg (ideal body weight), greater than 10 years of use, liver problems, kidney problems and age over 60.

When hydroxychloroquine toxicity is detected stopping the medication often halts the progression. The rheumatologist needs to be consulted before stopping the medication.

Many patients like Karen have found plaquenil to help their medical condition tremendously. Fortunately toxicity is rare and nowadays detected early.