Novel acoustic evaluation system for scratching behavior in itching dermatitis: rapid and accurate analysis for nocturnal scratching of atopic dermatitis patients

Quantitative analysis of itching in patients with itching dermatitis including atopic dermatitis (AD) is indispensable for the evaluation of disease activity and response to therapy. However, the objective evaluation system for itching is limited. We have developed a new objective and quantitative scratching behavior detection system using a wristwatch-type sound detector. The scratch sound detected on the wrist is recorded on a personal computer through a filtering, squaring and smoothing process by specific hardware. Subsequently, the data is automatically processed and judged for the scratching movement using specific software based on the periodicity and energy of the signal. Twenty-four measurements for healthy volunteers and those with AD by this system were evaluated by comparison with a simultaneously recorded video analysis system. The ratio of scratching time in sleeping time evaluated by these two systems was almost identical. The healthy subjects scratched their skin approximately 2 min during 6 h of sleeping time, while the mean scratching time of AD subjects was 24 min in their sleeping time. In contrast to the time-consuming video analysis system, this system takes only several minutes for evaluation of an overnight record. This scratch sound detection system is expected to serve as a new objective evaluation tool for itching dermatitis, namely, AD, and development of anti-itch therapies for dermatitis.

Bepotastine besilate for the treatment of pruritus

INTRODUCTION

Bepotastine besilate 1.5% is a newly approved second-generation topical antihistamine indicated for the pruritus associated with allergic conjunctivitis. In Japan, the oral formulation is approved to manage pruritus associated with allergic rhinitis and urticaria.

AREAS COVERED

Bepotastine is a piperidine derivative that antagonizes H1 receptors with high selectivity. It has been labeled a dual-acting or multiple-acting antiallergic medication, because it inhibits histamine at H1 receptors and stabilizes mast cells to prevent histamine release. Bepotastine may also have other immunoactive properties, such as inhibition of eosinophil migration, interleukin-5 (IL-5), leukotrienes (e.g., LTB4) and platelet-activating factor (PAF). Human clinical trials demonstrate the efficacy and safety of systemic and ophthalmic bepotastine for pruritus relief, limited penetration across the blood-brain-barrier and kinetics suitable for twice-daily administration.

EXPERT OPINION

Bepotastine besilate 1.5% ophthalmic solution is a safe and effective treatment option for allergic conjunctivitis associated pruritus. Side-effect profile is similar to other ocular antihistamine agents. Additional comparative-effectiveness studies would further advance its clinical use. Oral bepotastine is a safe and effective treatment option approved in Japan for allergic rhinitis, urticaria and pruritus associated with skin diseases.

Effects of bepotastine and fexofenadine on histamine-induced flare, wheal and itch

BACKGROUND

Urticaria is mainly caused by mast cell-derived histamine through the histamine H(1) receptor. Antihistamines are occasionally used on demand upon a recurrence of urticaria; therefore, rapidly acting agents should be explored. The onset of action is assumed to depend on time to maximum concentration (T(max)), but the speed of action needs to be evaluated not only through blood concentration analysis but also by measuring in vivo effectiveness.

METHODS

In this study, we chose two representative second-generation antihistamines (bepotastine and fexofenadine) with relatively short T(max) values and evaluated their effects on histamine-induced skin responses using both visual and laser Doppler imaging scales.

RESULTS

Suppression of histamine-induced flare and itch was observed 3 and 6 h after administration of both antihistamines. Attenuation of itch was seen 30 min after the administration of each drug and thereafter until 6 h. In addition, bepotastine suppressed flare formation after only 30 min following application.

CONCLUSION

These results suggest that antihistamines suppress histamine-induced itch and flare, followed by wheal formation, and that bepotastine suppresses skin symptoms sooner after administration than fexofenadine does, which is relatively consistent with the T(max) results.

Evaluation of itch by using NC/NgaTnd mice: a model of human atopic dermatitis

Atopic dermatitis (AD) is the extremely complicated syndrome that various abnormalities develop in a heap. There are various factors in patients for the onset and exacerbation of AD, including genetic cofactors of individuals, environmental factors, the failure of the skin barrier function, unfavorable regulation of the immune system, and the hypersensitivity of sensory nerves. In recent years, there have been many trials of the drug discovery that targets itch, because itch is one of the most serious clinical symptoms of AD. The selection of the suitable animal model that represents the condition of patients, as well as innovative analyzing protocols that can precisely evaluate itch, is indispensable for investigation of an effective drug for AD. In the paper, the unique spontaneous animal model for AD (NC/NgaTnd mice) and the novel quantification system of the laboratory animals that may bring a great progress in the future study of itch are outlined.

Oral bepotastine: in allergic disorders

Oral bepotastine is a second-generation histamine H(1) receptor antagonist that also suppresses some allergic inflammatory processes. Numerous short- and long-term clinical trials and surveillance studies have shown that twice-daily bepotastine is an effective and generally well tolerated antihistamine in the treatment of patients with allergic rhinitis, chronic urticaria or pruritus associated with skin conditions (eczema/dermatitis, prurigo or pruritus cutaneus). Bepotastine 20 mg/day was significantly more effective than terfenadine 120 mg/day in patients with perennial allergic rhinitis, as evaluated by the final global improvement rating and several other endpoints in a phase III trial. In phase III trials in patients with chronic urticaria, bepotastine 20 mg/day was more effective than placebo in improving levels of itching and eruption, and as effective as terfenadine 120 mg/day with regard to the final global improvement rating and other endpoints. In a noncomparative trial in patients with pruritus associated with skin diseases, the majority of bepotastine recipients in the overall population, as well as in the specific skin disease subgroups (eczema/dermatitis, prurigo or pruritus cutaneus), had a final global improvement rating of moderate or greater. Bepotastine was generally well tolerated in adult and paediatric patients with allergic conditions.

Non-clinical pharmacology, pharmacokinetics, and safety findings for the antihistamine bepotastine besilate

SCOPE

The purpose of this review is to examine published non-clinical literature on the antihistamine bepotastine besilate, including pharmacokinetic and pharmacologic properties.

METHODS

Standard literature searches using diverse databases were used to find articles on bepotastine besilate published between 1997 and 2009. Articles primarily described non-clinical data utilized for the development of an oral formulation of bepotastine besilate and were published in Japanese. No publications of non-clinical data for an ophthalmic formulation were found in the database searches.

FINDINGS

Bepotastine besilate is a second-generation antihistamine drug possessing selective histamine H(1) receptor antagonist activity. Bepotastine has negligible affinity for receptors associated with undesirable adverse effects, including histamine H(3), α(1)-, α(2)-, and β-adrenergic, serotonin (5-HT(2)), muscarinic, and benzodiazepine receptors. Bepotastine possesses additional anti-allergic activity including stabilization of mast cell function, inhibition of eosinophilic infiltration, inhibition of IL-5 production, and inhibition of LTB(4) and LTD(4) activity. Bepotastine in vivo dose-dependently inhibited the acceleration of histamine-induced vascular permeability and inhibited homologous passive cutaneous anaphylaxis in guinea pig studies. In mouse models of itching, oral bepotastine inhibited the frequency and duration of scratching behavior. Multiple in vivo animal toxicology studies have demonstrated bepotastine to be safe with no significant effects on respiratory, circulatory, central nervous, digestive, or urinary systems. The concentration of bepotastine after intravenous administration of bepotastine besilate (3 mg/kg) in rats was lower in the brain than in plasma, predicting reduced sedation effects compared to older antihistamines.

CONCLUSION

Non-clinical in vitro and in vivo studies have demonstrated bepotastine is a histamine H(1) receptor antagonist with favorable pharmacokinetic, pharmacologic, safety, and antihistamine properties as well as operating on other pathways leading to allergic inflammation beyond those directly involving the histamine H(1) receptor.

Bepotastine besilate, a highly selective histamine H(1) receptor antagonist, suppresses vascular hyperpermeability and eosinophil recruitment in in vitro and in vivo experimental allergic conjunctivitis models

To elucidate the ocular pharmacological properties of bepotastine besilate, a selective histamine H(1) receptor antagonist, when compared with other histamine H(1) receptor antagonists, using guinea pig allergic conjunctivitis models and in vitro models of eosinophil recruitment and mast cell membrane stabilization. Conjunctival vascular hyperpermeability was studied in guinea pigs passively sensitized with anti-ovalbumin antiserum or following subconjunctival injection of histamine. Modulation of eosinophil recruitment was evaluated for both platelet-activating factor (PAF)-induced eosinophil infiltration in guinea pigs and leukotriene B(4)-induced in vitro chemotaxis of guinea pig peritoneal eosinophils. Membrane-stabilizing effects of bepotastine also were studied with rat peritoneal mast cells stimulated with the ionophore A23187. Histamine H(1) receptor antagonists including bepotastine besilate were topically administered before ovalbumin, histamine or PAF challenges for in vivo experiments or were added directly to mast cell and eosinophil medium in vitro. Bepotastine besilate significantly inhibited conjunctival vascular hyperpermeability in a dose-dependent manner with maximal effect for bepotastine besilate 1.5%. In separate in vivo experiments, bepotastine besilate 1.0% was significantly more effective than levocabastine 0.025% in the passive sensitization model or olopatadine 0.1% in the histamine-induced hyperpermeability model. Bepotastine besilate 1.0% further suppressed PAF-induced eosinophil infiltration into conjunctival tissue more effectively than ketotifen 0.05%. Chemotaxis of guinea pig peritoneal eosinophils and histamine release from rat peritoneal mast cells in vitro were also inhibited by addition of bepotastine. Olopatadine had a weak effect as compared to that of bepotastine on eosinophil chemotaxis and no effect on mast cell histamine release in our study conditions. Bepotastine besilate was more potent than olopatadine, ketotifen, or levocabastine in reducing vascular hyperpermeability in various animal models of allergic conjunctivitis. Mast cell function and eosinophil chemotaxis were also inhibited in vitro with bepotastine, suggesting bepotastine acts as an inhibitor of allergic response through multiple mechanisms: histamine H(1) receptor antagonism, mast cell stabilization, and inhibition of eosinophil migration to ocular inflammatory sites.

Effect of epinastine hydrochloride on murine self-scratching behavior after skin-scratching stimulation

The itch-scratch cycle aggravates chronic inflammatory skin diseases. We have previously reported that mice begin to scratch themselves within several minutes after skin-scratching stimulation. This is associated with an increase in release of substance P (SP) from sensory nerve fibers in the skin, and the self-scratching behavior is suppressed by neurokinin-1 receptor (NK-1R) antagonist. Thus, SP may play a pivotal role in self-scratching behavior. The purpose of this study was to investigate the effect of second-generation histamine H(1)-receptor antagonists on self-scratching behavior in mice. After oral administration of epinastine hydrochloride (epinastine) (total dose 50 +/- 5 mg/kg for 7 days) or the vehicle only to ICR mice for 7 days, skin-scratching stimulation was administered to the dorsal skin for 10 min. Self-scratching behavior was recorded by video camera for 10 min. Twenty-four hours later, skin tissue was harvested and stained with toluidine blue. Immunohistochemical staining for SP was performed, and SP and nerve growth factor (NGF) concentrations were measured by enzyme-linked immunosorbent assay. Self-scratching behavior, mast cell degranulation, and NGF concentration decreased, and the length of SP-positive nerve fibers and SP concentrations increased significantly in the epinastine-treated group, when compared with the vehicle control group. We conclude that epinastine inhibits mast cell degranulation by attenuating SP release from sensory nerve fibers, which results in inhibition of self-scratching behavior. These results suggest that second-generation histamine H(1)-receptor antagonists might efficaciously control itch-scratch cycle-related skin diseases.