Receptor-selective retinoids for psoriasis: focus on tazarotene

Topical and oral retinoids have been successfully used in antipsoriatic therapy over the last 50 years. Development of more selective agents has led to an improved efficacy and safety profile. The first topical receptor-selective retinoid to be approved for the treatment of plaque psoriasis is tazarotene. Topical tazarotene displays an onset of action and efficacy similar to those of other established antipsoriatic agents. Common adverse events of this agent such as pruritus, burning, local skin irritation, and erythema are limited to the skin and generally mild or moderate in severity. Although effective as monotherapy, evidence is accumulating that combining topical tazarotene with other established antipsoriatic therapies results in enhanced efficacy and reduced adverse events. In particular, concomitant use of topical tazarotene with a mid-potency or high-potency corticosteroid in the treatment of psoriatic plaques enhances efficacy and reduces the risk of corticosteroid-induced skin atrophy. Combination of phototherapy with tazarotene accelerates the clinical response and diminishes the cumulative UVB or psoralen plus UVA (PUVA) exposure load. Recently, an oral form of tazarotene has been developed. The results of completed phase III clinical trials of this agent indicate a beneficial effect in moderate to severe plaque psoriasis. Adverse events are generally of mild severity, and most of those observed, such as cheilitis and dry skin, are typical of hypervitaminosis A. Of note, oral tazarotene appears not to be associated with other adverse events that are typical of oral retinoids, including hypertriglyceridemia and hypercholesterolemia. However, since head-to-head trials with acitretin (the only retinoid currently approved for systemic therapy) have not been conducted, it is unclear whether tazarotene is any safer or more effective than acitretin. Moreover, the major drawback of oral tazarotene is teratogenicity, which may limit its use in female patients. Further studies evaluating long-term clinical outcomes with oral tazarotene and its use in combination therapies are awaited.