A reappraisal of the use of 5‐methoxypsoralen in the therapy of psoriasis

Abstract

5-methoxypsoralen (5-MOP) is considered an alternative to 8-methoxypsoralen (8-MOP) for photochemotherapy of psoriasis. We have compared the clinical efficacy and tolerability of 5-MOP (1.2 mg/kg)-UVA versus 8-MOP (0.6 mg/kg)-UVA therapy in 25 patients of skin type III and IV, affected by relapsing plaque-type psoriasis of similar body involvement; indeed, the same patients were given 8-MOP during 1 year and 5-MOP during the subsequent year after relapsing. Both treatments cleared psoriatic lesions with a comparable number of exposures, but 5-MOP required significantly higher cumulative UVA doses. The difference was due to the lower phototoxicity of 5-MOP, as assessed by the determination of the minimal phototoxic dose, and to its higher tanning activity, as assessed by the weekly grading of pigmentation. Nevertheless, therapy by 5-MOP-UVA seemed particularly interesting in that it showed a higher tolerability since only 1 patient experienced nausea, whereas during therapy with 8-MOP-UVA nausea and/or vomiting occurred in 7 patients, sunburn in 6 and itching in 3. Since we have treated the same patients with the two drugs, our results were not influenced by interindividual variations of phototoxic responses, tanning ability and susceptibility to develop psoralen-induced short-term side-effects. It was concluded that, although long-term side-effects of the 5-MOP-UVA treatment have still to be determined, such treatment of psoriasis should be reappraised due to its higher tolerability in comparison to 8-MOP-UVA treatment.

Italian guidelines on the systemic treatments of moderate‐to‐severe plaque psoriasis

“…During maintenance treatment, an assessment of treatment goals • Active psoriatic arthritis • Psoriasis associated with severe symptoms (e.g. itch, burning) that are not controlled by topical therapies Table 4 Small-molecule drugs, including conventional and phototherapy for the treatments of chronic plaque psoriasis [20][21][22][23][24][25][26][27][28][29] Other label indications Italian guidelines on psoriasis Italian guidelines on psoriasis should be made in intervals given by the safety monitoring recommendations (usually every 8-12 weeks). In the case that the goal is not met, there are several strategies that may increase efficacy such as increasing the dose, reducing the time interval between administrations or adding another drug (combination therapy).…”

Comparing biological therapies in psoriasis: implications for clinical practice

“…Psoralen plus ultraviolet A (PUVA) photochemotherapy has been used for the treatment of psoriasis since the 1970s. The evidence base for PUVA therapy is of variable quality, and assessment of the data is complicated by the existence of different administration modalities for the psoralen (systemic, or topical using bath or cream) 3–14 . However, the majority of studies reviewed in the European Guidelines show good efficacy, with in some cases up to 90% of patients achieving a Psoriasis Area Severity index (PASI 75) response (patients achieving ≥75% improvement in PASI score compared with baseline, also known as the PASI 75 score).…”

The pharmacokinetics of 8‐methoxypsoralen following i.v. administration in humans [see comments]

“…protective glasses. In PUVA therapy, some acute minor effects have been reported, depending on the 8-MOP formulation and dose administered: nausea (3% to 51%) [16][17][18], headache (2%) [16], dizziness (1.5%) [16], pruritus (14% to 71%) [16,17]. A higher and earlier peak concentration has been observed when side effects were present (417 ng ml-' vs 280 ng ml-) [19].…”