Topical drugs containing corticosteroids are recommended first-line treatment for patients with mild-moderate psoriasis. However, the optimal recommended dosage of topical drugs has not been well established.
Objectives
To investigate the effect of topical drug application quantity and treatment duration on psoriasis treatment outcome.
Methods
We conducted a post-hoc analysis of two randomized controlled trials investigating 214 patients with psoriasis using topical drugs containing corticosteroids and/or calcipotriol for up to 48 weeks. We measured the amount of topical drugs used during the study period and calculated the mean amount of applied drugs per 1% affected body surface area (BSA) divided by number of days in the study period. Improvement in severity of psoriasis was measured by Lattice-System Physician's Global Assessment (LS-PGA) (where affected BSA was divided into seven categories) from baseline to last study visit. Descriptive results were reported as counts with proportions, and as means with normality-based confidence intervals (CI). Associations were analyzed using linear regressions.
Results
Most study participants had a duration of psoriasis greater than 20 years, moderate psoriasis, and no history of using systemic psoriasis treatment. They had applied a mean of 1.0 g per 1% BSA per day (95% CI 0.9; 1.2). Daily use of topical drugs for four-weeks reduced severity of psoriasis. However, extended daily use for up to 48 weeks provided further reduction in disease severity (coefficient --0.30 (95% CI -0.51, -0.09)) and -0.73 (95% CI -1.09; -0.38) (P= 0.028). Greater amount of applied topical drugs reduced severity of psoriasis in a linear manner. Every increase of 1 g of topical drugs applied per 1% BSA per day reduced LS-PGA by 0.43 (95% CI 0.24; 0.61). Finally, patients who had never used systemic drugs experienced a greater reduction in psoriasis when applying the same mean amount of topical drugs (coefficient -0.7 (95% CI -1.1, -0.4) compared to those who had a history of taking systemic treatment (-0.3 (95% CI -0.5; -0.1), P=0.026).
Conclusions
A mean application amount of at least 1.0 g of topical drugs per 1% BSA per day seems safe and effective and can be used daily until clearance.
