A double blind, randomized, controlled clinical trial to assess the efficacy of a new coal tar preparation (Exorex) in the treatment of chronic, plaque type psoriasis

Exorex is a new topical formulation for the treatment of psoriasis; it cont ains 1% coal tar and a synthetic analogue resembling components identified in banana skin (a complex of esterified essential fatty acids). To determin e whether the esterified essential fatty acid complex confers any therapeut ic advantage over coal tar alone, patients with chronic plaque psoriasis (n = 20) were entered into a double-blind, randomized, right/left comparison of Exorex, and Exorex without the essential fatty acid component (known her eafter as coal tar control) for 8 weeks. Target plaques were scored (0-4) f or erythema, desquamation and infiltration at day 0 and at 2 week intervals throughout the study. No significant differences were detected between Exo rex and coal tar control with respect to changes in the summed scores at ba seline and following 8 weeks of treatment (mean difference in summed score changes from baseline between Exorex and coal tar control 0.2, 95% confiden ce interval - 0.44 to 0.84; P = 0.52) or in the area under the response-tim e curve (P = 0.16). Mean percentage improvement in summed scores of target plaques were 53.9% (SE = 4%) and 56.1% (SE = 4.9%) for Exorex and coal tar control, respectively. Results suggest that the complex of esterified essen tial fatty acids is not exerting any clinically important therapeutic effec t in the treatment of chronic plaque psoriasis.