Tranexamic acid may also be taken orally for the treatment of melasma. Tranexamic acid is antifribrinolytic (i.e., it enhances clotting) and it is FDA  approved for heavy menstrual cycles. It is not FDA approved for melasma, and  therefore it is used off label when prescribed by a dermatologist. However, tranexamic acid has been shown to be an effective oral therapy for stubborn  cases of melasma. Tranexamic acid works by inhibiting plasmin which reduces  growth and pigment production of melanocytes.  Side effects are usually mild and include GI upset, headache, muscle aches, and  decreased menstrual blood flow. These occur in about 5 to 10 % of patients. In a  large study of 2000 subjects, one patient developed a deep venous thrombosis  (i.e., blood clot) while taking tranexamic acid however it was discovered that the  patient also had protein C and S deficiency which is an underlying predisposing  factor for blood clots.  Most patients have rebound hyperpigmentation when stopping oral tranexamic  acid and therefore need maintenance therapy.  The typical treatment course is for three months and is dosed at 325 mg twice  daily. It comes as a 650 mg tablet and you will need to use a pill cutter to chop it  in half. As tranexamic acid has a 12-hour half-life it must be dosed twice daily.