Tranexamic acid (trans-4-aminomethylcyclohexane-carboxylic acid) works by inhibiting the conversion of plasminogen into plasmin. This substance is released when the skin suffers some type of aggression such as sun exposure and acne inflammation. Plasmin stimulates inflammatory factors which in turn increase the production of melanin, by inhibiting this substance, the production of melanin is automatically inhibited, providing a lightening effect on the skin. Plasminogen is responsible for increasing the activity of melanocytes in vitro, and blocking this effect may be the paracrine mechanism for reducing melasma hyperpigmentation. Therefore, tranexamic acid has been studied as an effective alternative for the treatment of melasma.

Melasma is an acquired chronic hypermelanosis, characterized by brownish macules on photo-exposed areas of the skin, mainly the frontal and malar regions. It affects both sexes, with a higher incidence in women, especially pregnant women. It occurs in all races, particularly in individuals with high skin types, who live in areas with high levels of ultraviolet radiation (UV). UV radiation is an important factor, involved in the peroxidation of lipids in the cell membrane, with the release of free radicals, which would stimulate melanocytes. There are numerous factors involved in the etiology of the disease: genetic influences, exposure to UV radiation, pregnancy, hormonal therapies, cosmetics, phototoxic drugs, endocrinopathies, stress, among others.