Coal tar soothes psoriasis: New formulation effective, cosmetically acceptable

March 1, 2009

A new coal tar treatment for psoriasis sidesteps major formulation challenges that hindered patient acceptance of previous coal tar products, a clinical investigator says.

Key Points

"The concept behind this product (Psorent, NeoStrata) was to try to reformulate the liquor carbonis distillate (LCD) component of tar in order to decrease staining and improve the product's cosmetic acceptability," says Alexa Boer Kimball, M.D., M.P.H., associate professor of dermatology at Harvard Medical School, director of Massachusetts General and Brigham & Women's Hospitals' Clinical Unit for Research Trials in Skin (CURTIS), and a study co-author.

In terms of staining and cosmetic acceptability, she says, "The manufacturer did a very good job, which showed up preliminary results of our study."

For the study, researchers enrolled 60 otherwise healthy adult patients with moderate chronic plaque psoriasis involving 3 percent to 15 percent of their body surface area, excluding the scalp, face, palms, soles and groin. Researchers also excluded patients who had undergone topical psoriasis treatment within two weeks prior to the study's start, as well as those who had undergone phototherapy or oral therapy within the previous four weeks, or systemic immunomodulatory therapy within the previous 12 weeks.

Investigators divided the study population into two groups of 30 patients. They instructed patients in group one to apply the study medication, which contains 15 percent LCD in a lightweight, fast-drying vehicle, twice daily. Patients in group two applied calcipotriol cream 0.005 percent (Dovonex, Leo Pharma) twice daily.

Investigators (blinded to which medication patients had used) performed evaluations at baseline, then at two, four, eight and 12 weeks thereafter using the Psoriasis Area Severity Index (PASI), adjusted for exclusion of patients' scalp psoriasis, and a physician's global assessment (PGA). Evaluators also took digital patient photos at each visit and observed and recorded any adverse events.

Additionally, patients assessed their own results using a pruritus scale, the Dermatology Life Quality Index (DLQI) and a self-assessment questionnaire that addressed effectiveness, tolerability and overall satisfaction with treatment.

Results

At press time, 48 patients (26 females, 34 males; average age: 48.4 years) had completed the 12-week treatment cycle, Dr. Kimball says.

At this point, the proportion of LCD-treated patients who reached PASI 50 (50 percent or greater PASI improvement) was 14 of 23 (61 percent), versus 10 of 25 (40 percent) in the calcipotriol-treated group (p>0.10), she says.

Regarding PASI 75, significantly more patients in the LCD-treated group (30 percent) achieved this response than did patients in the calcipotriol-treated group (zero of 25; p<0.05). Likewise, mean PASI scores improved 55 percent with LCD treatment, compared to 39 percent with calcipotriol (p<0.10).

Patient assessments showed that the LCD solution reduced redness/irritation, itch and burning significantly faster than calcipotriol (week 2, p<0.05). At week 12, LCD performed better than calcipotriol in reducing redness/irritation (p<0.05).

Furthermore, Dr. Kimball says PGA scores improved for both treatment groups over the 12-week study period. At week 12, for example, the LCD-treated group improved 45 percent over baseline, versus 29 percent in the calcipotriol-treated group (p = 0.054). Both treatments significantly reduced pruritus and improved mean DLQI scores versus baseline, although researchers uncovered no statistically significant differences between treatments in these areas, she says.

Additionally, both treatments proved to be well-tolerated, Dr. Kimball tells Dermatology Times.

"I was pleasantly surprised by how much patient acceptance there was for this product. It really has overcome a number of the major formulation problems with tar treatments," she says.

Indeed, at week 12 both treatments scored in the "very good" range on a nine-point patient assessment scale with respect to ease of use, speed of absorption, speed of drying and patient comfort.

Moreover, patients rated the LCD solution's dab-on applicator between "very easy" and "extremely easy" to use at all time points.

"Coal tar has a long and fascinating history. It's been used for centuries, and before the advent of steroids, it was one of the few things we had in our armamentarium" that worked against psoriasis, Dr. Kimball says.

Disclosure: Dr. Kimball has received consulting fees from NeoStrata within the past year.

For more information: http://www.psoriasissolution.net/