By
Jonathan Yoken, MD
MONITORING
FOR PLAQUINIL-INDUCED
RETINAL TOXICITY
Plaquenil
is used for the treatment of malaria, systemic lupus erythematosus,
rheumatoid arthritis, and other inflammatory and connective tissue
diseases. Retinal toxicity from Plaquenil is of serious concern
because even after cessation of the drug there is little if any
visual recovery, and sometimes a progression of visual loss over
several years after the drug has been stopped. Fortunately, retinal
toxicity from plaquinil is quite rare relative to the number of
individuals taking the medication. Over a long period of time,
the drug may have a cumulative affect on the retinal pigment epithelium
(RPE). The RPE is responsible for the health of the retina, and
damage may lead to permanent visual loss. The drug also has a
toxic effect on photoreceptors in the retina. No medical therapy
has proven effective in Plaquenil toxicity other than cessation
of the drug. There may be a stage of very early functional loss
where cessation of the drug will allow a reversal of the toxicity.
However significant clinical recovery does not typically occur
after changes can be observed on examination of the macula. These
changes typically affect the RPE, and cause a ring of depigmentation
to develop in the center of the macula called bull's eye maculopathy.
There appears
to be minimal risk of toxicity for individuals using less than
6.5 mg/kg of hydroxychloroquine or 3 mg/kg of chloroquine for
less than 5 years. Hydroxychloroquine has been prescribed typically
at a dosage of either 200 or 400 mg/day, because of the tablet
size, rather than on a per weight basis. A 200 mg daily dose will
be relatively safe for all but extremely small individuals (less
than 68 pounds or 31 kg, if of average build), but a daily dosage
of 400 mg puts anyone under 135 pounds (62 kg) in the higher-risk
category.
The baseline
and subsequent eye examination includes Amsler Grid examination,
Humphrey 10-2 visual field test, color vision test and color photographs
of the retina. If a baseline examination is normal and dosages
are at the relatively safe levels, screening during the next 5
years can be at the frequency of regular ophthalmic examinations.
Annual screening during the first 5 years of usage is recommended
only for individuals who are at higher risk because of their higher
dosage, duration of use (more than 5 years), or other complicating
factors (kidney or liver disease, obesity).
Reference:
Recommendations on screening for chloroquine and hydroxychloroquine
retinopathy - a report by the American Academy of Ophthalmology
Ophthalmology 2002 Jul;109(7):1377-82.
