The influence of psoriatic plaques pretreatment with crude coal tar vs. petrolatum on the efficacy of narrow-band ultraviolet B: a half-vs.-half intra-individual double-blinded comparative study.

The value of psoriatic plaques pretreatment with specific topical preparations in the setting of NB-ultraviolet-B (UVB) therapy is debatable. It may be clarified through a comparative assessment between crude coal tar and petrolatum as pretreatment candidates. A prospective study included 40 patients with plaque psoriasis undergoing NB-UVB therapy. We compared among three treatment regimens: NB-UVB alone (control group; n=20) as well as NB-UVB preceded by crude coal tar 3% on one side and petrolatum on the other side (cases group I and II; n=20). Tar and petrolatum were topically applied thrice/day the day before NB-UVB exposure. Applications were removed using olive oil directly before NB-UVB exposure. Regimens' frequency was thrice/week and the clinical outcome was assessed, through both psoriasis area and severity index (PASI) and physician global assessment (PGA) scores, at baseline and 3 months later. There were significant (P<0.01) decreases in both PASI and PGA scores in all the groups. In comparison with the controls, cases revealed significantly (P<0.05) higher improvement percentages in both PASI and PGA scores for both tar and petrolatum. This influence, through the PGA score, was significantly (P<0.05) in favor of petrolatum. The pretreatment of psoriatic plaques with either petrolatum or crude coal tar may enhance the therapeutic outcome of NB-UVB, which appeared to favor petrolatum.