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