Increasing the quantity of topical corticosteroids applied reduces the severity of psoriasis: results from two...

Topical drugs containing corticosteroids are the recommended first-line treatment for mild-to-moderate psoriasis, although the optimal dosage has not been established.

To investigate the effect of topical drug application quantity and treatment duration on psoriasis treatment outcomes.

We conducted a post hoc analysis of two randomized controlled trials investigating 214 patients with psoriasis treated using topical drugs containing corticosteroids and/or calcipotriol for up to 48 weeks. We measured the quantity of topical drugs used during the study period and calculated the mean quantity of applied drugs per 1% affected body surface area (BSA) divided by the number of days in the study period. Improvements in psoriasis were measured using the Lattice System Physician's Global Assessment (LS-PGA) (where affected BSA is categorized into seven levels) from baseline to final visit. Descriptive results were reported as counts with proportions and as means with normality-based confidence intervals (CIs). Associations were analysed using linear regressions.

Most study participants had a duration of psoriasis > 20 years, moderate psoriasis and no history of receiving systemic psoriasis treatment. They applied a mean of 1.0 g per 1% affected BSA daily (95% CI 0.9-1.2). Daily use of topical drugs for 4 weeks reduced the severity of psoriasis, while extended daily use for up to 48 weeks provided further reductions in disease severity (coefficients -0.30, 95% CI -0.51 to -0.09 and -0.73, 95% CI -1.09 to -0.38, respectively; P = 0.03). Increasing the quantity of topical drugs applied reduced psoriasis severity in a linear manner. Each increase of 1 g of topical drugs applied per 1% affected BSA daily reduced LS-PGA by 0.43 (95% CI 0.24-0.61). Patients who had never received systemic drugs experienced a greater reduction in psoriasis when applying the same mean quantity of topical drugs (coefficient -0.7, 95% CI -1.1 to -0.4) compared with patients with a history of systemic treatment (-0.3, 95% CI -0.5 to -0.1; P = 0.03).

The application of a mean quantity of at least 1.0 g of topical drugs per 1% affected BSA daily is safe and effective and can be used daily until clearance.