First of all, let's talk about the pharmacological effects of this drug: Psoralen belongs to furan coumarin, and Psoralen and its derivatives are phototoxic substances, which can not directly produce melanin, but can specifically absorb ultraviolet rays, produce photobiological effects, and achieve therapeutic purposes. Its mechanism is: enhancing the skin's action on ultraviolet rays, increasing the density of epidermal melanocytes, oxidizing reduced melanin into melanin, and promoting its diffusion; Destroy sulfhydryl compounds in skin through skin inflammatory reaction, activate tyrosinase activity, increase melanin synthesis and transportation, and restore pigment; Stimulate keratinocytes to release melanocyte growth promoting factors, so that the remaining melanocytes in epidermis or hair follicles can proliferate; Eliminate the expression of vitiligo-related antibodies on melanocytes and block the damage to melanocytes. Usage and dosage: for adult patients with extensive skin lesions, oral administration is generally adopted, and long-wavelength ultraviolet radiation is carried out after taking the medicine; For adults and children with less skin lesions, after external use, long-wave ultraviolet radiation will produce erythema. Intramuscular injection. 2ml once, 1-2 times a day, 10 days as a course of treatment, or as directed by the doctor. For the treatment of vitiligo, about 1 hour after injection, the affected area is irradiated with artificial ultraviolet rays for 1- 10 minutes or exposed to sunlight for 5-20 minutes; If local redness and blisters appear, the medication should be suspended; Occasionally dizziness and high blood pressure after taking the medicine; Use with caution in patients with hypertension; It is not suitable for pregnant women.