A Comprehensive Monograph on Hydroxychloroquine (DB01611)

Introduction: The Enduring and Evolving Role of a 4-Aminoquinoline

Hydroxychloroquine (HCQ) is a synthetic 4-aminoquinoline drug that occupies a unique and significant position in modern medicine.[1] Its development during World War II was driven by the need for antimalarial agents with a more favorable safety profile than earlier compounds like quinacrine and its direct chemical parent, chloroquine.[3] A serendipitous discovery during its widespread use revealed its profound immunomodulatory properties, a finding that fundamentally altered its clinical trajectory.[4] This led to its repurposing and eventual establishment as a cornerstone therapy in the management of chronic autoimmune diseases, most notably Systemic Lupus Erythematosus (SLE) and Rheumatoid Arthritis (RA).[1]

The drug's clinical utility is defined by a dual identity: it functions as both an anti-infective agent for specific malarial parasites and as a Disease-Modifying Antirheumatic Drug (DMARD) capable of regulating the underlying processes of autoimmune conditions rather than merely palliating symptoms.[2] Its profound impact on patient outcomes, particularly in lupus, and its broad utility have secured its place on the World Health Organization's List of Essential Medicines.[1] Its extensive use is reflected in its prescription volume, ranking as the 112th most commonly prescribed medication in the United States in 2022 with over 5 million prescriptions filled.[1]