May 1, 2009 A new Cochrane review finds that two commonly used topical treatments work best together to treat chronic psoriasis, but are not a cure.
“Almost everyone with psoriasis will try topical treatments and some people will use them throughout their lifetime, so it is important to know how effective and safe they are,” said lead author Anne Mason, a research fellow at the Centre for Health Economics the University of York, in England.
Mason said that chronic plaque psoriasis is the most common form, “typically affecting 1 to 2 percent of the population.” Psoriasis causes thick, red patches — or plaques — and silver scales to form on the skin. Topical treatments are those applied directly to the skin.
This review looked at a wide range of different topical treatments from 131 randomized trials involving 21,448 people with psoriasis. Treatments include synthetic versions of vitamin D called “analogues,” topical corticosteroids and tar-based medications among others. Researchers compared treatments with either a placebo or a vitamin D product, depending on the study.
“The main message from the review is that most topical treatments are effective in reducing the symptoms of psoriasis, but none actually cures psoriasis,” Mason said.
The review appears in the latest issue of The Cochrane Library, a publication of The Cochrane Collaboration, an international organization that evaluates medical research. Systematic reviews like this one draw evidence-based conclusions about medical practice after considering both the content and quality of existing medical trials on a topic.
“Another key finding is that combining two commonly used topical treatments — vitamin D analogues and a corticosteroid — is more effective than either treatment used on its own,” Mason said. “Using the two products separately, vitamin D in the morning and corticosteroid at night, can achieve similar effects, and be as well tolerated, as using a specially combined product.”
Up to 40 percent of those who used vitamin D treatments had skin irritation and other side effects that led to lower levels of compliance. The topical corticosteroids showed less irritation, but had higher levels of thinning of the skin.
Mason noted that psoriasis is a lifelong disease, so patients likely will be using prescribed medications for very long periods. However, since most of the studies only followed participants between four and eight weeks, the authors were unable to come to any conclusions about extended use of these treatments.
“It is surprising how little adequate evidence is available addressing long-term safety of treatments or long-term management of psoriasis,” Mason said. “Patients should realize that most evidence is from short-term trials and that there is very little long-term evidence on benefits and potential harms to consider when deciding on maintenance strategies.”
Steven Feldman, M.D., is a professor of dermatology, pathology and public health sciences at Wake Forest University. “The goal of therapy for psoriasis is to strike a balance between the irritation sometimes seen with Vitamin D analogues and thinning of the skin that is an adverse effect of long-term corticosteroid use,” he said. “This study makes it clear scientifically that there will be no one-size-fits-all solution in treating this condition. The review is an evidence-based confirmation of what most of us knew from experience.”
While the results show that the corticosteroids work as well as the Vitamin D products with fewer short-term side effects, he cautioned against interpreting this review as a call to forego the more expensive Vitamin D analogues.
“The idea that corticosteroids are safer somehow is misleading,” Feldman said. “That doesn’t take into account that the more serious side effects that occur with long-term continuous use of the corticosteroid drugs.”
The review disclosed that three of its five co-authors have received funding from pharmaceutical companies that make medications used to treat psoriasis.
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- Mason AR, et al. Topical treatments for chronic plaque psoriasis. Cochrane Database of Systematic Reviews, 2009, Issue No. 2
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