Psoriasis is a disorder of both the innate and the adaptive immune systems, which lead to sustained inflammation [8]. Typical clinical manifestations of skin lesions are scaly erythema or plaques, localized or widely distributed. As far as now, advances in the treatment of psoriasis have been limited [1, 8].
Datura metel L., as a traditional Chinese medicine, has been used to anesthetize patients for at least one thousand years. Since 1970, the alkaloids in Datura metel L. have been made into injections and used widely as general anesthetics. During 1980 to 1988, Datura metel L. injection was applied to treat psoriasis. Unfortunately, in the late 1988, Datura metel L. was limited as toxic drug by the government and no longer used as before. Up to date, barely no case report can cure psoriasis and finding a cure for psoriasis is urgent.
Interestingly, we find the articles which record the methods and results in treating psoriasis by Datura metel L. injection, and the range in cure rate from 28% to 67% [10-14]. Intravenous therapy for psoriasis is using a mixture of analgesic and phenothiazine derivatives as a premedication in advance before applying Datura metel L. injection in anesthesia. Patients can sleep deeply for 6 to 8 hours and wake up naturally [11-14]. Oral therapy for psoriasis is taking Datura metel L. capsules with or without using diazepam to put the patient to sleep half hour later [9,11,20]. In this meta-analysis, the case cure rate in intravenous therapy is higher than that in oral therapy, and the effective rate in both are closely (Figure 1, 2). In those cured cases, most patients stopped itching as soon as they woke up from anesthesia, and had significant desquamation in 3 to 7 days, the skin lesions completely or nearly completely disappear in 1 to 3 months [11-14]. Adverse effects from Datura metel L. therapy could be treated or avoided. According to the considerable cure or effective rate, Datura metel L. therapy might be a promising treatment for patients suffering from psoriasis, particularly for the severe or recalcitrant types.
Given the period in which these studies were conducted, the quality of clinical studies was not high (Table 2). However, the case reports described complete diagnosis and treatment in details, which can give confidence in the results [13,14]. As the psoriasis area and severity index (PASI) wasn’t been proposed at that time, the researchers used their own agreed-upon criteria to determine efficacy, resulting in high heterogeneity (Figure 1, 2). Hence, large sample size and control groups with unified criteria should be executed in further studies.
Nevertheless, the mechanism of the Datura metel L. therapy is still under research. More and more effective components in Datura metel L. have been found, with antispasmodic, analgesia, anti-inflammatory, immunosuppressive, anti-allergic, and other pharmacological effects [23]. Scopolamine and atropine are the main components of the total alkaloids in Datura metel L., inhibit the cerebral cortex and some parts under the cortex, accelerate the heart rate, dilate blood vessels, and improve the brain microcirculation [24]. These functions might improve the microcirculation of skin lesions and regulate the immune system through the nervous systems (in hypothesis). The withanolides in Datura metel L. regulate both angiogenesis and inflammation, including sphingolipid metabolism and HIF-1-α/VEGF pathway [25]. These researches studied the possible effects of Datura metel L. in the treatment of psoriasis, but the mechanism was not clarified. Moreover, it is important to find effective components of Datura metel L., reduce toxicity and increase efficiency for clinical application. This is probably the most promising drug for psoriasis.
This study had some limitations. Firstly, high heterogeneity existed in outcomes, and lots of factors could lead to heterogeneity, such as differences among various therapy regimens, disease type, disease stage, age, and evaluation criterion. Second, as single-arm trials lacked control groups, the comparison between other treatments was based on data from the population with a discrepant baseline.