A new aqueous dithranol gel for psoriasis: Comparison with placebo and calcipotriol ointment

A new aqueous dithranol gel has been developed to reduce irritation and staining by minimizing unwanted dithranol residue on the skin surface. Left-right paired comparisons were conducted vs placebo (phase I) in 12 inpatients and vs calcipotriol ointment (phase II) in 25 inpatients with symmetrical chronic plaque psoriasis to assess its efficacy and acceptability. In phase I, dithranol gel was significantly better than the placebo after 4 weeks treatment for each severity parameter, erythema, scale and palpability (P 0.022). Combined severity scores (maximum 9) fell from 6.3 to 1.1 with dithranol and to 4.1 with placebo. In phase II, calcipotriol produced significantly greater improvement after 3 weeks than dithranol gel, but there was no difference after 4 weeks by which time severity scores fell from 6.3 to 2.2 with dithranol and to 1.8 with calcipotriol. There was a greater reduction in psoriasis area (P=0.04) with calcipotriol but no overall difference in the patients' assessment of effectiveness for either treatment after 4 weeks use. At 4 and 12 weeks follow-up there was no objective difference in severity, although more patients thought that the calcipotriol-treated sites showed greater deterioration. Calcipotriol caused less irritation and staining than dithranol gel (P< 0.001). Dithranol in an aqueous gel formulation was effective for inpatient treatment of chronic psoriasis and acceptable for patients, but showed a higher incidence of irritation and staining than calcipotriol ointment. (Dermatol Treat (1997) 8: 11–15)