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Mahonia ointment in the treatment of psoriasis

Oregon grape (Mahonia aquifolium (Pursh) Nutt., Berberidaceae) is frequently cited in traditional herbal literature as an effective treatment for psoriasis vulgaris, a proliferative skin disorder of uncertain etiology. The chronic nature of psoriasis generally necessitates long-term treatment, and standard therapeutic agents are often associated with safety concerns.

Topical ointments containing Mahonia bark extract are now marketed in Europe for psoriasis. Results of recent in vitro trials utilizing human keratinocytes suggest that Oregon grape bark extract as well as the consitutents berberine, berbamine, and oxycanthine have antiproliferative, antioxidant and antiinflammatory effects relevant to psoriasis.

Based on this evidence and their own unpublished preliminary findings, these German investigators designed a randomized placebo-controlled study to evaluate the efficacy of an ointment containing 10% Mahonia bark extract in psoriasis of all severity gradings (mild to severe). Eighty-two patients with psoriasis were instructed to apply the Mahonia and placebo ointments two or three times a day, one ointment on the right side of the body and the other on the left, and to wear ointment-soaked bandages at night. Body sides were randomly assigned to Mahonia ointment or placebo, which consisted of the ointment base. According to the authors, their chosen trial design is standard in dermatology research.

Average length of treatment was four weeks, after which physicians and patients assessed treatment efficacy utilizing a three-step scale: "symptoms unchanged," "symptoms improved", and "symptoms disappeared completely." Based on patient efficacy assessments, there were some statistically significant differences between the Mahonia and placebo ointments, but overall, more than half of both patients and physicians judged the Mahonia ointment as ineffective. Among treatment responders, Mahonia was particularly effective in moderately severe psoriasis, and the investigators concluded that Mahonia bark ointment is "a potent and safe therapy of moderately severe cases of psoriasis vulgaris." Side effects, including itching, burning, and allergic reactions, were reported by four patients.

Study shortcomings cited by the authors include unspecific inclusion criteria (allowing inclusion of extremely severe and long-standing cases of psoriasis), a "crude" main effect measurement scale that might not be sensitive to small changes, and possible patient errors, such as confusion about the assignment of body sides and failure to adequately wash hands between applications of the two ointments. The relatively "high number" of treatment nonresponders was attributed to the inclusion of extremely severe cases of psoriasis.
-- Evelyn Leigh, HRF

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[Wiesenauer, M., and Ludtke, R. 1996. Mahonia aquifolium in patients with Psoriasis vulgaris -- an intraindividual study. Phytomedicine, Vol. 3, 231-235.]

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[Muller, K., Ziereis, K., Gawlik, I. 1995. The antipsoriatic Mahonia aquifolium and its active constituents; II. Antiproliferative activity against cell growth of human keratinocytes. Planta Med, Vol. 61, 74-75.]

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