Introduction: Post-inflammatory hyperpigmentation (PIH) after solar lentigo removal using a Q-switched (QS) 532-nm Nd:YAG laser is a cause for concern. This study aimed to evaluate the efficacy and safety of intradermal injections of tranexamic acid (TA) at reducing the risk of PIH after QS 532-nm Nd:YAG laser treatment of solar lentigines.

Methods: Twenty-five patients with 50 solar lentigines on forearms underwent QS 532-nm Nd:YAG laser treatment. Then, TA (50 mg/mL) was injected randomly into one lesion and 0.9% normal saline was injected intradermally into another lesion. Two blinded dermatologists and a Mexameter® evaluated photographs at baseline, and at weeks 2, 4, 8, and 12.

Results: At the end of the study, the mean melanin index (MI) had decreased significantly in both groups. The TA group showed a significant reduction in the mean MI compared with that in the control group at week 4 (p = 0.025). The overall PIH rates were 16% and 28% in the TA and control groups, respectively. The side effects of TA were minimal and they were resolved within 1 h.

Conclusion: Single dose of intradermal TA (50 mg/mL) injected can reduce the risk of developing PIH 4 weeks after 532-nm QS Nd:YAG laser treatment of solar lentigines.