Duration of the antihistaminic effect after discontinuation of ebastine

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.

Ebastine in allergic rhinitis and chronic idiopathic urticaria

Histamine is a key mediator in the development of allergy symptoms, and oral H(1)-antihistamines are among the most widely used treatments for symptomatic relief in conditions such as allergic rhinitis and chronic urticaria. Ebastine is a second-generation antihistamine which has been shown to be an effective treatment for both seasonal and perennial allergic rhinitis. In controlled clinical trials in adult and adolescent patients with allergic rhinitis, ebastine 10 mg once-daily improved symptoms to a significantly greater extent than placebo and to a similar extent as loratadine 10 mg and cetirizine 10 mg (both once-daily), while ebastine 20 mg proved to be more effective than these two comparator antihistamines. In addition, ebastine was significantly more effective than placebo at relieving the symptoms of chronic idiopathic urticaria. Ebastine provides efficacy throughout the 24-h dosing interval with once-daily administration and clinical benefit is seen from the first day of treatment. Small studies have found beneficial effects for ebastine in patients with other disorders, including cold urticaria, dermographic urticaria, atopic asthma, mosquito bites and (in combination with pseudoephedrine) the common cold. In addition to the regular ebastine tablet, a fast-dissolving tablet (FDT) formulation, which disintegrates in the mouth without the aid of a drink, is also available. It has been shown to be bioequivalent to the regular tablet, and to be significantly more effective than desloratadine at reducing histamine-induced cutaneous wheals. A number of patient surveys demonstrated that the majority of individuals who tried the fast-dissolving formulation reported it to be convenient for use, fast-acting and preferred it to their previous antihistamine medication. Perhaps most importantly, a large proportion of patients indicated that they would prefer to use this new formulation in the future. Ebastine has a rapid onset of action and it can be administered once-daily, with or without food. Dose modifications are not needed in elderly patients, or in those with renal or mild to moderate hepatic impairment. Ebastine is generally well-tolerated, and clinical studies showed that at usual therapeutic doses of 10 and 20 mg once-daily, it had no clinically relevant adverse effects on cognitive function and psychomotor performance or on cardiovascular function. In conclusion, ebastine is an effective and generally well-tolerated treatment for allergic rhinitis and chronic idiopathic urticaria. In addition to the regular tablet formulation, ebastine is available as a FDT, providing a treatment option that is particularly convenient for patients.

Inhibition of allergen-induced wheal and flare reactions by levocetirizine and desloratadine

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

The reproducible and standardized histamine-induced wheal and flare model helps identify the objective effectiveness of antihistamines in humans, as well as their differences in onset and duration of action. Some of the newest antihistamines have already been compared in a head-to-head setting using this model. However, their objective action at inhibiting the allergen-induced wheal and flare response has not been reported yet.

WHAT THIS STUDY ADDS

The time-response study presented here shows the objective activity of two of the newest generation of antihistamines, levocetirizine and desloratadine, at inhibiting the allergen-induced wheal and flare response in a randomized, cross over, placebo-controlled trial. This model is interesting to the clinical setting since allergic subjects are recruited, and the response to allergen involves mast cell degranulation and release of numerous vasoactive and pro-inflammatory mediators additionally to histamine. In addition, this study reports receptor occupancy for both antihistamines at therapeutic dosage, leading to analysis of potential differences in activity. This study clearly shows the potential anti-inflammatory properties of desloratadine and levocetirizine in their skin activity when allergen is the challenging agent as occurs in the clinical situation.

AIMS

To evaluate the inhibitory activity of the new-generation antihistamines levocetirizine and desloratadine at their therapeutic doses on the allergen-induced wheal and flare reaction at 1.5 h, 4 h, 7 h, 12 h and 24 h postdose, and to measure their plasma and skin concentrations.

METHODS

A double-blind, randomized, cross-over, placebo-controlled study in 18 allergic subjects was carried out. The time-response of the wheal and flare reaction areas under the curve (AUC) were compared by anova.

RESULTS

Both antihistamines significantly (P < 0.001) inhibited the allergen-induced wheal and flare reactions compared with placebo. Levocetirizine was significantly more potent than desloratadine. Mean +/- SEM wheal AUC(0-24 h) was 506.4 +/- 81.0 with levocetirizine and 995.5 +/- 81.0 mm(2) h with desloratadine as compared with placebo (1318.5 +/- 361.0 mm(2) h). Flare AUC(0-24 h) was 5927.3 +/- 1686.5 and 15838.2 +/- 1686.5 mm(2) h, respectively [P < 0.001 for both compared with placebo (22508.2 +/- 7437.1 mm(2) h)]. Levocetirizine showed significant inhibition of wheal and flare already at 1.5 h postdose compared with placebo (P <or= 0.001); desloratadine achieved a significant effect only after 4 h. The mean total plasma concentration at 12 h and 24 h after intake was higher for levocetirizine (58.1 +/- 13.4 and 20.0 +/- 8.1 ng ml(-1), respectively) as compared with desloratadine (0.82 +/- 0.24 and 0.45 +/- 0.16 ng ml(-1)). Similarly, higher mean unbound skin concentrations were observed for levocetirizine 24 h after intake (1.80 ng g(-1)) than for desloratadine (0.07 ng g(-1)). This was associated with greater receptor occupancy for levocetirizine (54%) than desloratadine (34%) at 24 h.

CONCLUSIONS

Levocetirizine suppressed the cutaneous allergic reactions with a higher potency than desloratadine, which correlated with its high receptor occupancy. Receptor occupancy rather than drug affinity or plasma half-life is more representative of antihistamine potency.

A review of the second-generation antihistamine ebastine for the treatment of allergic disorders

Ebastine is a once-daily, non-sedating, selective, long-acting, second-generation antihistamine. The use of ebastine is indicated in patients suffering from intermittent and persistent allergic rhinitis and chronic idiopathic urticaria. Ebastine 10 mg/day, appears as effective as other second-generation antihistamines, such as cetirizine and loratadine. Ebastine 20 mg/day is indicated in patients with moderate and severe allergic symptoms. No cardiovascular effects of ebastine are described, although there is a pharmacokinetic interaction when ketoconazole or macrolides are co-administered. Ebastine has no relevant effects on the psychomotor performance. Even with ebastine 20 mg/day skilled performance does not appear to be impaired. Furthermore, ebastine 5-10 and 2.5 mg, appears to be efficient and can be used safely in children 6-11 and 2-5 years of age, respectively. Ebastine appears to be a safe, effective and well-tolerated second-generation antihistamine in the treatment of allergic rhinitis and chronic idiopathic urticaria.