Comparison of indirubin concentrations in indigo naturalis ointment for psoriasis treatment: a randomized, double-blind, dosage-controlled trial

Abstract

Background

Indigo naturalis and its refined formulation, Lindioil, are effective in treating psoriatic symptoms topically. Indirubin is the active ingredient in indigo naturalis.

Objectives

To determine the efficacy and safety of different concentrations of indirubin in Lindioil ointment for treating psoriasis.

Methods

In this randomized, double-blind trial, adult patients presenting with chronic plaque psoriasis for >1 year and with <20% of the body surface area (BSA) affected were randomized to apply Lindioil ointment containing 200 μg/g, 100 μg/g, 50 μg/g, or 10 μg/g of indirubin twice daily for 8 weeks followed by an additional 12-week safety/extension period. The primary endpoint was the mean percentage change in Psoriasis Area and Severity Index (PASI) score along with the proportion of subjects achieving 75% and 90% reductions in PASI scores (PASI75 and PASI90, respectively) from baseline to week 8.

Results

The results from week 8 revealed that the 200 μg/g group had the greatest reduction in PASI score (69·2%, 95% confidence interval [CI] 82·8–55·5), followed by the 100 μg/g group (63·1%, 95% CI 73·5–52·8), the 10 μg/g group (53·4%, 95% CI 64·0–42·8), and the 50 μg/g group (50·3%, 95% CI 63·2–37·4), with between-group comparison of P = 0·0445). The highest proportion of the subjects in the 200 μg/g group achieved PASI75 (56·5%, P = 0·0474) and PASI90 (30·4%, P = 0·0098). No severe treatment-related adverse events were reported during the 20-week evaluation.

Conclusions

200 μg/g of indirubin in Lindioil ointment is the most effective concentration studied so far for treating psoriasis topically, and is safe ClinicalTrials . gov Identifier: NCT01735864

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