Chloroquine Toxicity in OphthalmologyThese days the so-called second line drugs are being used more aggressively in the management of the arthritidies. More and more, we find our patients on Gold Salts, Methotrexate and Chloroquine. In medical school we were taught that Chloroquine was particularly toxic to the eye, and that close supervision was mandatory. Several points need to be made with respect to the anti-malarials and their toxicity to the eye: In the past, the fears of toxicity were based on the total accumulated dosage the patient ingested over his lifetime. This now appears not to be a problem, if the actual effective doses are adhered to. For Chloroquine (Aralen) the maximum dose is 6mg/kg/24hrs. For HydroxyChloroquine the dose is 4.5mg/kg/24hrs. Above these doses the patient is being overdosed, and toxicity may appear. Chloroquine is more toxic than Hydroxy Chloroquine, but it also is a more effective anti-inflammatory. Virtually 90% of patients on Chloroquine will show corneal changes when examined with a slit lamp and the pupil dilated. It has been suggested that this can actually be used as an index of effective dose. Potential retinal toxicities can be screened for using the Ishara color plates and Amsler grid testing. Patients are given an Amsler grid and test at home twice a week. The earliest change is a relative scotoma in the paracentral area [inside 10 degrees fixation]. Early relative scotoma is not in itself a contraindication to continuation of the drug. Approximately 10% of scotomata will progress. The development of scotomata is however, an indication for more close monitoring, and if the value of the scotoma is deepening, then the drug might be discontinued. The role of the Ophthalmologist is to monitor the function of the retina in patients on the drug. Decisions on whether the drug must be discontinued are best left to the clinician. There is no urgency about early consultation when the drug is initiated. Assessment within the first year of treatment is adequate. And that's the Berries.
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