• Clinical science

Chloroquine and hydroxychloroquine


Chloroquine and hydroxychloroquine are drugs derived from the quinoline molecule. Both are used as antimalarial blood schizonticides, and hydroxychloroquine is also frequently used as an antirheumatic. Their mechanism of action is not entirely understood. However, despite their varying therapeutic dosage and toxicity, both drugs have similar clinical indications and side effects. One of their most serious side effects is retinal toxicity, referred to as 4AQ retinopathy or chloroquine retinopathy, which must be screened for in all cases of long-term use.


  • Widely-accepted mechanisms of action
    • Anti-malarial action: : the drugs accumulate in the parasite's food vacuole inhibit polymerization of heme; into hemozoin and form the heme-chloroquine complex, which is highly toxic to the schizont → lyse membranes and kill the parasite
    • Anti-rheumatoid action: these drugs interfere with "antigen processing" in macrophages and other antigen-presenting cells → decrease the formation of peptide-MHC protein complexes → down-regulate the immune response against autoantigenic peptides


Side effects


We list the most important adverse effects. The selection is not exhaustive.