Effect of salicylic acid on the activity of betamethasone-17,21-dipropionate in the treatment of erythematous squamous dermatoses.

Forty adult out-patients with erythematous squamous dermatoses of the scalp were treated in this 21-day double-blind study with an alcohol base lotion containing either 0.05% betamethasone-17,21-dipropionate, 2% salicylic acid, 0.05% betamethasone-17,21-dipropionate + 2% salicylic acid or their respective placebo. The four treatments were assigned randomly to the patients according to a 2 x 2 orthogonal factorial design. Changes in severity of redness, scaling, pruritus and size of lesions were evaluated. Since very few patients presented with excoriation and lichenification, these symptoms could not be ascertained. Results were assessed for significance by covariance analysis where initial status was used as regressor. A potentiation of the betamethasone-17,21-dipropionate activity by salicylic acid was observed for scaling. An additive effect was noted for redness and pruritus. According to the physician's global evaluation, patients treated with the combination drug showed a better evolution than those treated with placebo. The results suggest that addition of a keratolytic agent enhances the corticosteroid effect in the treatment of erythematous squamous dermatoses.