Local skin inflammatory and allergic lesions – a clinician’s perspective

Currently on Polish market there are several medicinal products designed for therapy of contact dermatitis accompanied by urticaria. Contact dermatitis may be caused by exposure to exogenous substances that elicit an immune response, resulting in inflammation in the skin and mucous membranes. Most of them contain antihistamines; therefore, their action is delayed. From a clinician’s perspective this therapeutic approach may not be sufficient to fully address the needs of patients.
In recent years an interesting therapeutic option has been reintroduced to the Polish market. A topical gel containing diphenhydramine hydrochloride 20 mg/g and lidocaine hydrochloride 10 mg/g is marketed for the symptomatic treatment of contact allergic and inflammatory skin lesions accompanied by itching, responding to treatment with antihistamines and resulting from external factors.
Scientific justification for such a combination is solid. Diphenhydramine hydrochloride (DH) selectively binds to histamine 1 receptors, thereby blocking the actions of endogenous histamine [1]. Therefore, DH could be effec­tive in treating histamine-mediated skin conditions. Lidocaine (LH) is a locally acting anaesthetic that binds to sodium channels located in the membrane of nerve cells, inhibiting the depolarisation process and the generation of an action potential. LH application may provide relief in less than 2 minutes [2-4]. The activity of the combination of these active substances in the symptomatic treatment of local pain and pruritus could be based on their different mechanisms of action. Lidocaine blocks pain and itching, while diphenhydramine has an antihistamine effect and thus reduces the formation of a histamine-dependent inflammatory reaction. In summary, an additive effect of these 2 active substances should be expected.
To the author’s best knowledge, most data available in public domain address the efficacy of separate components of this medicinal product but not its combination. There is one study with results provided by Marketing Authorisation Holder (MAH); these results are discussed below.
A randomised, double-blind, cross-over trial employed a pharmacodynamic model of diphenhydramine hydrochloride 20 mg/g and lidocaine hydrochloride 10 mg/g gel topical use versus placebo (product vehicle) in the treatment of local skin inflammatory and allergic lesions induced by a provocative test with histamine (skin prick test). Study included 44...


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