Chloroquine (CQ)
has been developed for the therapy of malaria. It’s an old drug as the substance
had already been discovered in 1934. You might know hydroxychloroquine (HCQ) Plaquenil
or Quensyl, which differs from chloroquine just by the presence of a hydroxyl
group. We use these antimalarials in rheumatology as DMARD (Disease Modifying Anti
Rheumatic Drugs) to treat rheumatoid arthritis (often in combination with
methotrexate), systemic lupus erythematodes (SLE), Sjoegren’s syndrome, and
others. A study in 1985 found a lower rate of retinopathy in hydroxychloroquine
when compared to chloroquine. As retinopathy is not reversible and as there is
no present therapy, we need to reduce the risk for the development of
antimalarial associated retinopathy.
In June 2016
the American Academy of Ophthalmology published recommendations on screening
for chloroquine and hydroxychloroquine retinopathy. They recommend a maximum
daily HCQ use of ≤5.0 mg/kg real weight. “The risk of toxicity is dependent on
daily dose and duration of use. At recommended doses, the risk of toxicity up
to 5 years is under 1% and up to 10 years is under 2%, but it rises to almost
20% after 20 years.” Higher dosage means higher risk, so we have to keep the
daily dosage down. Long duration of therapy with antimalarials is another significant
risk factor, so we must try to reduce the duration of this therapy. This might be
hard to achieve in lupus. Renal disease is another risk factor to look for, but
rheumatologists usually screen their patients for renal disease. And we have to
look for tamoxifen, as this drug increases the risk for chloroquine and
hydroxychloroquine retinopathy. This is sad to hear as the group
of patients needing tamoxifen is also the group, where other therapy options
like biologicals are contraindicated.
Risk
Reduction of Retinopathy:
·
adapted
dosage of CQ and HCQ
·
avoiding long duration of therapy
·
screening
for renal disease
·
monitoring
concomitant medication
·
screening
for retinopathy
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