Do excoriations in psoriasis delay or prevent the effect of topical treatment?

Anthralin: historical and current perspectives

Anthralin was first synthesized in 1916. Earlier, a natural product, chrysarobin, originally derived from the South American araroba tree, had been used to treat psoriasis. Anthralin was first used in Germany, and later in the Ingram regimen in Britain, but it has never been popular with American dermatologists. This is probably due to the side effects of staining and irritation of the skin. Attempts to reduce these using low concentration, short contact therapy, and concomitant steroid therapy, have been only partially successful. It may be that better instruction of patients and physicians will lead to wider use of this effective topical agent for the treatment of psoriasis. The mode of action of anthralin is thought to be either through its effect on deoxyribonucleic acid (DNA), probably mitochondrial DNA, which reduces cell turnover, or through its effects on various enzyme systems, including those of polyamine synthesis and respiration. The aims of this review are to discuss historical aspects of anthralin and to update its chemistry, pharmacology, and clinical usage.

Low strength anthralin in psoriasis

Anthralin in low concentrations (0.01%--0.03%) was applied in an ointment form once per day in the hospital to 130 psoriasis patients. The treatment program included also the use of UVB light, emollients and bath oil and an antihistamine. Clearing of psoriasis was achieved in all patients in an average time of 4 weeks. The involution of the lesions was carefully studied by correlated clinical observations, light microscopy, transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Striking healing of the holes in the stratum corneum and of the gaps in the basement membrane occurred. Low strength anthralin, in addition to its effectiveness, did not produce irritation, staining or side-effects.

A topical treatment program for psoriasis with low anthralin concentrations

A treatment program for psoriasis in which 0.01--0.05% anthralin was used has been clinically evaluated. In such low concentrations it is possible to use anthralin if one simultaneously avoids exposing the skin to unnecessary external mechanical trauma, including the mechanical removal of the scales from the lesions. Applied in this fashion, anthralin then also becomes most suitable for use in ambulatory therapy. In these low concentrations it does not irritate either the involved or the non-involved psoriatic skin. No discoloration of the clothes, the skin, the hair or the nails was observed.

Light and electron microscopy of excoriated psoriatic lesions in patients during topical treatment

This is a light- and electron-microscopic study of excoriated, recalcitrant psoriatic lesions in ambulatory patients undergoing topical treatment. During regeneration of a stratum corneum without scales, in areas showing excoriations bounded by a non-cornified epidermis, horny cell layers, designated I and II, are formed. In areas in which excoriations are delimited by an epidermis with a retained stratum corneum, the latter is composed of a horny cell layer I and/or II or III. The horny cell layers differ, as shown by light- and electron-microscopy. In the less fresh excoriations, a homogeneous substance, which includes fibrin deposits, is observed. This substance is also seen frequently in the stratum corneum. In the less fresh excoriations and in the stratum corneum there are numerous polymorphonuclear leukocytes. In these locations, however, they are only found simultaneously with the homogeneous substance containing fibrin deposits. Polymorphonuclear leukocytes are also seen in the dermal papillae and in the non-cornified epidermis, particularly in the macroscopically "old" excoriations. The changes observed in these recalcitrant lesions have been interpreted as secondary and are believed to be expressions of a non-specific reaction to the mechanical damage to which the ambulatory patients have constantly exposed the lesions. They are not interpreted as changes in the psoriatic condition per se.