C₈H₁₅NO₂  

Prevent and/or treat pigmentations such as chloasmas, freckles, sunburn, dark skin and

melanoderma caused by a drug such as steroid

Act on the chronic mild inflammatory condition at the sites of spots, to suppress

melanocyte activation

Decreases melanocyte tyrosinase activity by preventing the binding of plasminogen to the

keratinocytes, which results in reduction of prostaglandins and arachidonic acid, which are

inflammatory mediators involved in melanogenesis.

It is generally thought that biosynthesis of melanin occurs in a cytoplasmic 

granule, melanosome, in the melanocyte via a complex pathway in which

 tyrosine is oxidized by tyrosinase to cause biosynthesis of dopa and

dopaquinone, and the dopaquinone is converted into indolequinone or the

like due to auto-oxidation by ultraviolet rays.

It has become clear that melanin, which so far has been considered to be

formed only in melanocytes, is also formed outside of melanocytes.
It was found that the quick skin darkening under the sun is due to the

colorless pre-melanin DHICA (precursor of melanin) which has accumulate

in the epidermis is converted to melanin upon exposure to ultraviolet A

rays  (long wave length).
When transparent DHICA solution was irradiated with UVA equivalent to

about 20 minutes of exposure to sunlight in the summer, pre-melanin was

converted to melanin in a short time.

At the sites where spots develop, excessive melanin formation constantly

takes place. It was found that inflammatory cells are more abundant at the

site of the spot than at the normal site (the inflammation at the spot site is

extremely slight and does not manifest as redness, swelling or pain). It was

also discovered that the number of activated melanocytes

(melanin-producing cells) to total melanocytes is higher at the spot site

than at the normal site. From these results, we may assume that melanocytes remain activated because of "a chronic, mild inflammatory condition"

and excessive melanin formation thus persists at the site of the spot.

Pigmentations such as chloasmas (or melasma), freckles, sunburn, dark skin and

melanoderma caused by a drug such as steroid are generated by excess deposition of

melanin pigment in the skin.
Melasma is an acquired symmetric hyperpigmentation characterized by irregular light- to

gray-brown macules, especially on the face of women.

Tranexamic acid is an antifibrinolytic agent and is used to control excess bleeding. The skin

whitening effects of tranexamic acid was occasionally found when it was used as a coagulant to

treat aneurismal subarachnoid hemorrhage. And from then on, it was used in physician's

prescription to treat liver spots and pigmentation.
The most famous example is that tranexamic acid has been widely used in Shiseido’s whitening

series products such as NAVISION IP Essence (TA), NAVISION TA Lotion, NAVISION TA

Essence and Melanoreduce EX

TA has been used clinically for over 30 years to treat abnormal bleeding, as well as skin diseases such as eczema, hives, drug-induced irritation,

and

toxicodermia, via internal administration, and also orally to treat itching,

swelling, and erythema. It is a representative ω-amino aci-type

anti-plasmin agent that has a highly specific action on the fibrinolytic

system,  blocking the conversion of plasminogen to plasmin by inhibiting PA action through the formation of a reversible complex with

plasminogen. TA is also thought to form a reversible complex with

plasmin, inhibiting the reaction with  fibrin.

Kondou et al. have published results from a clinical study examining the

effects of a tranexamic acid (TA) emulsion applied topically to melasma

and freckles. The study involved 33 subjects, 25 with melasma and 8 with

freckles, who applied the TA emulsion for five to eighteen weeks, after

which their skin pigmentation was visually assessed by a dermatologist.
Researchers found that the TA emulsion had improved the pigmentation

in 20 subjects with melasma (80%) and 6 subjects (75%) with freckles. No

side effect was recognized and thus the TA emulsion was deemed safe.

In regard to changes over the course of the study, marked improvement

was observed within eight weeks for melasma but within 12 weeks for

freckles; therefore, improvement was considered to require at least two

months of topical application. The authors concluded the TA emulsion

was an effective cosmeceutical that provided a whitening effect on

melasma and freckles  through inhibition of melanin synthesis. It also

prevented the appearance of new pigment spots and freckles.

In an open pilot study, intradermal microinjection of tranexamic acid was

given to 100 women with melasma for 12 weeks. The treatment was well

tolerated, and 76.5% of the subjects reported fair lightening of their

melasma.

Freely soluble in water and in glacial acetic acid, practically insoluble

in alcohol and in acetone