In vitro compatibility of tazarotene with other topical treatments of psoriasis.

Tazarotene is the first receptor-selective retinoid indicated for the topical treatment of plaque psoriasis. It is being used clinically in combination with other topical antipsoriatic treatments, although its stability in the presence of these products has not been examined extensively. This study examines the compatibility of tazarotene 0.05% gel with 17 other topical products used in the treatment of psoriasis, assessed over a 2-week period. Tazarotene showed minimal degradation (<10%) at 0, 8, 24, and 48 hours after compounding with each of the 17 products. In addition, after 1 and 2 weeks, degradation of tazarotene remained less than 10% for 15 of the 17 products tested. Tazarotene appeared to have minimal impact on the stability of the other products. These results suggest that tazarotene gel can be successfully coprescribed with a range of commonly used topical psoriasis treatments without adversely affecting the chemical stability of either agent.

Interactions between tazarotene and ultraviolet light.

Tazarotene in combination with phototherapy is being used clinically for the treatment of plaque psoriasis. This study investigates the dose of UVB light required to induce minimal erythema and the dose of UVA light required to induce immediate pigment darkening, with and without pretreatment with tazarotene 0.1% gel. The photostability of tazarotene is also assessed. Pretreatment with tazarotene 0.1% gel 3 times per week for 2 weeks before phototherapy significantly reduced the mean minimal erythema dose (MED) for UVB from 56.25 to 42.50 mJ/cm(2) (P <.01), and significantly reduced the mean UVA exposure required to induce immediate pigment darkening from 20.18 to 18.50 J/cm(2) (P <.05). A thin application of tazarotene gel immediately before phototherapy had no significant effect on the mean MED for UVB, whereas a thick application of the gel increased the MED slightly, from 56.25 to 62.50 mJ/cm(2) (P =.1). Tazarotene remained chemically stable when used in conjunction with UVB or UVA phototherapy. To reduce the patient's potential to burn or tan, we recommend initiating UVB phototherapy at 50% to 75% of the MED when it is used in combination with tazarotene. We also recommend initiating PUVA therapy at slightly lower doses than usual. Lower total doses of UVA or UVB may be needed when patients with psoriasis are treated concomitantly with tazarotene.