Hydroxychloroquine (Plaquenil): How does it work?

How does it work?

Hydroxychloroquine (HCQ) is an oral medication widely used for many types of inflammatory and autoimmune type conditions. "Plaquenil" is a popular trade name but there are many generics available. In the world of hair loss, these drugs are commonly used to treat scarring alopecias such as lichen planopilaris, frontal fibrosing alopecia, discoid lupus and pseudopelade.

How does the drug work? Hydroxychloroquine is mildly immunosuppressive. The precise mechanism of action has not been entirely elucidated but dozens of different mechanisms have been uncovered.

HCQ has an unusual property in that it accumulates in a specific area of cells known as “lysosomes” and “endosomes.” By doing so, it changes the pH in these compartments and interferes with the normal jobs that are supposed to go on inside these cellular compartments. Many cells of the immune system, including macrophages, lymphocytes and neutrophils, rely on their lysosomes to function properly.

As a result, HCQ interferes with a range of normal processes of the immune system including interfering with antigen processing.  They are known to 1) inhibit cytokine release of key molecules that activate the immune system (IL) 1, IL-2, IL-6, IL-18, tumor necrosis factor α, interferon γ) 2) decrease the activity of NK cells 3) affect neutrophil function 4) regulate apoptosis and 5) inhibit the activity of T cells.