Predicting and establishing the clinical efficacy of a histamine h(1)-receptor antagonist : desloratadine, the model paradigm

Desloratadine citrate disodium injection, a potent histamine H(1) receptor antagonist, inhibits chemokine production in ovalbumin-induced allergic rhinitis guinea pig model and histamine-induced human nasal epithelial cells via inhibiting the ERK1/2 and NF-kappa B signal cascades

Chemokines have chemotactic properties on leukocyte subsets whose modulation plays a pivotal role in allergic inflammatory processes. Our present study was designed to investigate the anti-allergic and anti-inflammatory properties of desloratadine citrate disodium injection (DLC) and elucidate the molecular mechanisms of its anti-inflammatory properties. The anti-allergic effects of DLC were evaluated based on allergic symptoms, serological marker production and histological changes of the nasal mucosa in guinea pigs model of allergic rhinitis. The anti-inflammatory properties and molecular mechanisms of DLC were explored by studying the regulation of a set of chemokines and extracellular signal-regulated kinase (ERK)1/2 and nuclear factor-kappa B (NF-κB) pathways, after DLC treatment in guinea pigs model of allergic rhinitis in vivo and histamine-activated human nasal epithelial cells (HNECs) in vitro. In vivo model in guinea pigs, DLC alleviated the rhinitis symptoms, inhibited inflammatory cells infiltration in nasal lavage fluid (NLF) and histamine, monocyte chemotactic protein (MCP)-1, regulated on activation normal T cell expressed, and presumably secreted (RANTEs) and interleukin (IL)-8 release in sera and P-ERK1/2 and NF-κB activation in nasal mucosa. In vitro, DLC markedly inhibited histamine-induced production of MCP-1, RANTEs and IL-8 and suppressed c-Raf, mitogen-activated protein/extracellular signal-regulated kinase kinase (MEK) and ERK1/2 activation in HNECs. These results provide evidence that DLC possesses potent anti-allergic and anti-inflammatory properties. The mechanism of action underlying DLC in allergic inflammation appears to be inhibition of the phosphorylation of ERK1/2, in addition to blocking of the NF-κB pathway.

Comparative efficacy and bioequivalence of novel h1-antihistamine bepotastine salts (nicotinate and salicylate)

Bepotastine salts (nicotinate and salicylate) were investigated for their physicochemical properties to develop novel salt forms of bepotastine, bioequivalent to the bepotastine besilate-loaded tablet (Talion). These bepotastine salts of either nicotinate- or salicylate-loaded tablets were prepared by conventional wet granulation method, and dissolution profiles and pharmacokinetics in beagle dogs were compared to those of Talion. A novel bepotastine nicotinate has a higher solubility at varying pH levels (1.2, 4, or 6.8) than salicylate-loaded or besilate-loaded salt. In addition, those bepostastine salt forms (nicotinate and salicylate) are stable in heat, light, and water. Further, the novel nicotinate- and salicylate-loaded tablets showed similar dissolution rates to Talion in several selected dissolution media and were bioequivalent to Talion in beagle dogs in terms of area under the concentration-time curve (AUC) and maximum observed concentration (Cmax). A pharmacokinetic study performed in beagle dogs demonstrated that test and reference products were found to be bioequivalent in terms of safety, efficacy, and pharmacokinetic properties. These results suggest that bepostastine nicotinate and salicylate formulations are considered applicable candidates and are well tolerated versus the conventional bepostastine besilate formulation.

Antihistaminic, anti-inflammatory, and antiallergic properties of the nonsedating second-generation antihistamine desloratadine: a review of the evidence

The allergy cascade presents widespread inflammatory and proinflammatory activation, robust cytokine and chemokine signaling, and heterogeneous immune and endothelial responses that lead ultimately to the manifestations of allergic reaction. Histamine, a small peptide with inherent vasoactive properties, is released from granules contained within mast cells, basophils, lymphocytes, and other reservoirs and interacts with histamine receptors to regulate numerous cellular functions involved in allergic inflammation and immune modulation. Of the known histamine receptors, the H(1)-receptor is most clearly associated with potentiation of proinflammatory immune cell activity and enhanced effector function and is the prime focus of suppressive therapy. Second-generation oral H(1)-antihistamines, such as cetirizine, desloratadine, fexofenadine, levocetirizine, and loratadine, are mainstays of allergy treatment, acting as highly specific, long-acting H(1)-receptor agonists at its unique receptor. The ongoing identification of immune effector cells and mediators involved in the allergic cascade indicates that further research is necessary to define the role of antihistamines such as desloratadine in anti-inflammatory therapy.

Ebastine in the light of CONGA recommendations for the development of third-generation antihistamines

In 2003 a consensus group on new-generation antihistamines (CONGA) defined the characteristics required for a third-generation H(1) antihistamine as there had been much controversy about this issue since the early 1990s. One of the antihistamines that had been claimed to belong to such a group is the second-generation antihistamine, ebastine. The objective of this review is to analyze the pharmacology of ebastine, in light of the CONGA recommendations for the development of new-generation antihistamines: (1) anti-inflammatory properties, (2) potency, efficacy and effectiveness, (3) lack of cardiotoxicity, (4) lack of drug interactions, (5) lack of CNS effects, and (6) pharmacological approach. Ebastine seems to have anti-inflammatory properties that help to ameliorate nasal congestion, though this has not yet been conclusively demonstrated. Its pharmacological-therapeutic profile does not differ greatly from that of other second-generation antihistamines. Its cardiac safety has been widely assessed and no cardiac toxicity has been found at therapeutic doses despite initial concerns. The risk of potentially relevant drug interactions has been investigated and ruled out. Ebastine does not produce sedation at therapeutic doses and drug interaction studies with classical CNS depressants have not demonstrated a synergistic effect. Pharmacologically, ebastine is an H(1) inverse agonist. Perhaps the answer to the quest for new-generation antihistamines lies not only in H(1) but in a combined approach with other histamine receptors.

Disposition of desloratadine in healthy volunteers

The absorption, metabolism and excretion of desloratadine (DL, Clarinex) were characterized in six healthy male volunteers. Subjects received a single oral 10-mg dose of [(14)C]DL ( approximately 104 microCi). Blood, urine and feces were collected over 240 h. DL was well absorbed; drug-derived radioactivity was excreted in both urine (41%) and feces (47%). With the exception of a single subject, DL was extensively metabolized; the major biotransformation pathway consisted of hydroxylation at the 3 position of the pyridine ring and subsequent glucuronidation (3-OH-DL-glucuronide or M13). In five of the six subjects, DL was slowly eliminated (mean t((1/2)) = 19.5 h) and persisted in the plasma for 48-120 h post-dose. This is in contrast to a t((1/2)) of approximately 110 h and quantifiable plasma DL concentrations for the entire 240-h sampling period in one subject, who was identified phenotypically as a poor metabolizer of DL. This subject also exhibited correspondingly lower amounts of M13 in urine and 3-OH-DL (M40) in feces. Disposition of DL in this subject was characterized by slow absorption, slow metabolism and prolonged elimination. Further clinical studies confirmed the lack of safety issues associated with polymorphism of DL metabolism (Prenner et al. 2006, Expert Opinion on Drug Safety, 5: 211-223).

Validation of guinea pig model of allergic rhinitis by oral and topical drugs

Ovalbumin-induced guinea pig model of rhinitis was assessed for its utility in the studies of rhinitis. Systemic sensitization and challenge with ovalbumin-induced rhinitis symptoms and an increase in anti-OVA-IgE and IgG titers, positive skin reactions and nasal lavage IL-4 concentration. Histopathology of nasal mucosa showed infiltration of eosinophils and other inflammatory cells consistent with the symptoms. Topical sensitization of ovalbumin yielded inconsistent symptoms of rhinitis. In systemic sensitization model, repeated challenge of ovalbumin caused similar response for at least 3 consecutive challenges. The symptoms were affected by relative humidity in the air and dosing volume of topical drugs. Sneezing and lacrimation were reduced by acute oral administration of the H1 receptor antagonists and steroids or the prophylactic oral administration of cysteinyl leukotriene (CysLT1) receptor antagonist montelukast or acute topical antihistamines, mast cell stabilizer sodium cromoglycate and anticholinergic agent ipratropium bromide, but not by a topical steroid. Nose rubbing was reduced significantly by some oral and topical antihistamines. Oral steroids offered excellent protection against all symptoms. Dexamethasone and montelukast also inhibited nasal lavage IL-4 concentration and inflammatory cell infiltration. Treatment with topical steroid fluticasone for 2 weeks had no effect on sneezing or rubbing. However, it caused complete inhibition of congestion. The cyclooxygenase inhibitor indomethacin had no effect on symptoms of rhinitis. The adrenergic alpha receptor agonist-decongestant oxymetazoline caused reduction in congestion. These results suggest that differential responsiveness to symptoms of rhinitis by a new agent can be very well profiled in the model in congruence with the mediation pathways and mechanism of action of drugs. The model provides complete symptomatic characterization of rhinitis and is a good tool for its study.