Neues zur Therapie des chronischen Pruritus

2020 guidelines for the diagnosis and treatment of cutaneous pruritus

The mechanisms underlying itch are not fully understood. Physicians usually encounter difficulty controlling itch in generalized pruritus. Since only a small percentage of patients with generalized pruritus respond to antihistamines (H₁ receptor antagonists), a variety of itch mediators and mechanisms other than histaminergic signals are considered to be involved in itch for these non-responsive patients. In 2012, we created guidelines for generalized pruritus. Those guidelines have been updated and revised to make some of the definitions, diagnostic terms, and classifications more applicable to daily clinical practice. Cutaneous pruritus as designated in these guidelines is a disease characterized by itch without an observable rash. Generalized pruritus (without skin inflammation) is defined as the presence of itch over a wide area, and not localized to a specific part of the body. This entity includes idiopathic pruritus, pruritus in the elderly, symptomatic pruritus, pregnancy-associated pruritus, drug-induced pruritus, and psychogenic pruritus. Localized pruritus (without skin inflammation) represents fixed itch localized to a specific part of the body, and includes anogenital pruritus, scalp pruritus, notalgia paresthetica, and brachioradial pruritus. These guidelines outline the current concepts and specify the diagnostic methods/treatments for cutaneous pruritus.

Ex vivo skin permeation and penetration of nonivamide from and in vivo skin tolerability of film-forming formulations containing porous silica

AIM

The purpose of this study was to evaluate skin permeation and penetration of nonivamide which has been formulated in novel film-forming formulations (FFFs). These formulations aim to prolong the availability of capsaicinoids which are used in long-term treatment of chronic pruritus.

METHODS

An oily solution of nonivamide was loaded into porous silica particles which then were suspended in an aqueous dispersion of a sustained release polymer. Permeation and penetration experiments were performed ex vivo with postauricular porcine skin using modified Franz diffusion cells. The penetrated drug amount was assessed ex vivo by skin surface biopsy followed by cryo-sectioning. Furthermore, in vivo skin irritation experiments were performed to compare the potential skin irritation caused by the FFFs to conventionally used semi-solid formulations.

RESULTS

Permeation rates of nonivamide from FFF through the skin are comparable to that from clinically used immediate release formulations. This elucidates the therapeutic safety profile of the novel FFF. Penetration studies confirmed the prolonged drug availability at the site of action. FFFs were found not to irritate the skin of healthy volunteers.

CONCLUSION

FFFs with sustained nonivamide penetration represent safe and easy-to-use formulations. They therefore may improve the treatment of chronic pruritus with capsaicinoids by enhancing patient compliance through a sustained release regime.