Vitamin D3 derivatives are a class of topical drugs developed in 1980 for the treatment of psoriasis, and are among the most commonly used and effective topical drugs in recent years. Vitamin D3 is continuously hydroxylated by liver and kidney to form the active metabolite osteotriol 21α, 252 dihydroxyvitamin D3, which plays an important role in maintaining calcium and phosphorus metabolism and bone mineralization in the body. osteotriol also regulates epidermal growth, keratinization and inhibits inflammation, inhibits the proliferation of keratinocytes and promotes their differentiation. Vitamin D3 derivatives include carbostriol, tacalcitol, etc. Some patients may have questions, isn’t vitamin D3 mainly related to the balance of calcium and phosphorus metabolism in the body and the mineralization of bone? Why can it treat psoriasis? Will it lead to high blood calcium in the body if used topically? And what is its mechanism for treating psoriasis? The new physiological function of vitamin D was discovered in this way: initially, when doctors in Japan used the vitamin D3 analogue rocuronium to treat an elderly patient with osteoporosis, they unexpectedly found that the original psoriasis lesions improved after 2 months. It was found that this was mainly because active vitamin D3 can bind to the vitamin D3 receptor in the body and can control the proliferation of skin keratin-forming cells, induce their differentiation and inhibit T-cell activation, while psoriasis is characterized by excessive proliferation of epidermal keratin-forming cells and excessive activation of T-cells within the lesions. Therefore, vitamin D analogues can be used for the treatment of psoriasis. However, the use of oral osteopontin is limited by the fact that it can cause hypercalcemia. Currently on the market, Darex and Mengfu are new vitamin D3 analogues, which have similar affinity with vitamin D3 receptors as ossifying triol and are directly applied to the skin to act on keratin-forming cells, but with little skin absorption, so they have very low effect on blood calcium, while retaining the role of vitamin D3 in regulating cell differentiation and inhibiting cell proliferation. Clinical application found that they are effective and comparable to corticosteroids, but do not contain hormones and have no side effects of hormones, so they were soon favored by doctors and patients and became a more ideal drug for psoriasis treatment. The application method is to apply thinly and evenly to the affected area, once a day in the morning and once in the evening. Most patients see the beginning of improvement in symptoms after 1-2 weeks of use, and the best results are usually obtained after 6-8 weeks of treatment. Treatment should be maintained once a day after the lesions have subsided. The use of Daralis ointment begins with a reduction in scaling of the affected area, followed by a flattening of the papules and finally a gradual fading of the erythema. This process can also be combined with corticosteroid ointment or other topical preparations to improve the efficacy and reduce side effects. In order to obtain better results, some experts proposed to use sequential therapy, divided into three stages: 1, clearing stage: 1 corticosteroid ointment such as halometasone cream in the morning, and topical calcipotriol ointment in the evening, for a total of 2 weeks; 2, transition stage: daily topical calcipotriol ointment from Monday to Friday, 2 times / day, Saturday and Sunday with corticosteroid cream for 2 days, 2 times / day, usually 2 weeks; 3, maintenance stage: single use of calcipotriol ointment, 2 times / day, usually 2 weeks; 3, maintenance stage: single use of calcipotriol ointment, 2 times / day. , maintenance phase: calcipotriol ointment alone, 2 times/day. Corticosteroids in sequential therapy are mainly strong and moderately effective, which may cause local atrophy, abnormal pigmentation, hirsutism, secondary infection and adverse reactions of capillary dilation if used for long-term treatment of psoriasis, but in sequential therapy, corticosteroids are used continuously in the first week, and the dosage is gradually reduced with the course of treatment until it is discontinued, while plaque psoriasis lesions are hypertrophic, and short-term intermittent use will not The short-term intermittent use does not produce significant side effects. From the results of treatment, the sequential treatment of plaque psoriasis with carbotriol cream and corticosteroid cream has good efficacy and has the advantages of fast onset of action, good efficacy and less side effects compared with topical carbotriol cream alone. Compared with Darex, Mengfu has less local irritation and can be applied to the face, but do not use it on the cornea and conjunctiva.