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.