Observer-blind, randomized, intrapatient comparison of a novel 1% coal tar preparation (Exorex) and calcipotriol cream in the treatment of plaque type psoriasis

Background In a recent pilot study a novel, patented fatty acid-based 1% coal tar preparation (Exorex) has been found to be similar in efficacy to calcipotriol in the treatment of psoriasis. Objectives Our aim was to investigate the therapeutic efficacy, safety and cosmetic acceptability of the new 1% coal tar preparation in comparison with calcipotriol cream in a larger patient cohort. Patients and methods Forty patients with chronic plaque type psoriasis were included in this randomized, observer-blind, intrapatient comparison trial. In each patient two comparable target plaques were treated twice daily with 1% coal tar preparation or calcipotriol cream. At the onset of therapy and at weeks 2, 4, 6 and 8, the response to treatment was determined by the psoriasis severity index (PSI) that assesses the degree of erythema, infiltration and scaling of the psoriatic lesions on a five-point scale. In addition, all treatment-related side-effects were recorded and cosmetic acceptability of both treatments was rated every second week by the patients. After complete or near complete clearing the patients were followed up until relapse or for a maximum period of 18 months. Results Thirty-eight patients completed the study. At termination of the trial the mean +/- SD baseline PSI score of 9.2 +/- 1.5 was reduced to 3.0 +/- 2.9 by 1% coal tar preparation and to 2.8 +/- 2.7 by calcipotriol. The mean PSI reduction between baseline and final assessment did not differ significantly between 1% coal tar preparation and calcipotriol (P = 0.77). The mean intraindividual difference in reduction of PSI score between 1% coal tar preparation and calcipotriol was 0.1 score points (95% confidence interval -0.84 to +0.63). No difference between either preparation was observed with regard to time until relapse. Itching was caused by 1% coal tar preparation in four patients and by calcipotriol in one patient. Unpleasant odour or staining of the 1% coal tar preparation was reported by six patients, whereas one patient complained about the smell of the calcipotriol cream. Conclusions The novel 1% coal tar preparation was found to be comparably as effective as calcipotriol in treating psoriasis. Tolerability and cosmetic acceptability was better for calcipotriol. Taking into consideration that the coal tar preparation is considerably less expensive than calcipotriol this new product appears as a very useful topical medication for chronic plaque type psoriasis.