NEW YORK (Reuters Health) Mar 04 - In patients with rheumatoid arthritis (RA) or systemic lupus erythematosus (SLE), long-term hydroxychloroquine therapy increases the risk of retinopathy, according to a February 12th online publication in Arthritis Care & Research.
For more than half a century, hydroxychloroquine has been widely used for these conditions, and "through all of this time, a central concern has been its potential for retinal toxicity," said the two authors, Dr. Frederick Wolfe of the National Data Bank for Rheumatic Diseases, Wichita, Kansas and Dr. Michael F. Marmor of Stanford University in California.
To help define the risk, they studied 3995 RA or SLE patients who had used hydroxychloroquine, including 1538 current users (474 with lupus and 1064 with RA). Patients who reported toxicity were followed up with detailed interviews and with confirmation by specialists.
Overall, 6.5% of lifetime hydroxychloroquine users discontinued therapy because of eye problems, and 1.8% did so because or retinal problems in particular. However, the researchers could document definite or probable toxicity in only 0.65%.
The risk of toxicity was low in the initial 7 years of exposure but increased roughly 5-fold after 7 years of use or 1000 grams of total exposure, the authors said. Toxicity was unrelated to age, weight, or daily dose.
Most current users had eye exams every 6 months (40.4%) or yearly (50.5%) to screen for toxicity. Only 2.1% reported never having a toxicity examination.
The researchers conclude that toxicity "is an infrequent event, even for long-term users; but the risk becomes increasingly significant beyond 5-7 years given that the outcome may be irreversible blindness."
In email to Reuters Health, Dr. Wolfe commented that "this paper defines the rate and risk factors for toxicity, and allows for rational monitoring by physicians."
Arthritis Care Res 2010.