Cetirizine and levocetirizine inhibit eotaxin-induced eosinophil transendothelial migration through human dermal or lung microvascular endothelial cells

Comparative clinical efficacy, onset and duration of action of levocetirizine and desloratadine for symptoms of seasonal allergic rhinitis in subjects evaluated in the Environmental Exposure Unit (EEU)

The Environmental Exposure Unit, an indoor pollen challenge system to test anti-allergic medications, was used to compare the onset and duration of action and the efficacy of levocetirizine and desloratadine, two recently developed H1-antagonists. In this double-blind, placebo-controlled, parallel-group study, qualified subjects were randomised to once-daily levocetirizine 5 mg (n = 141), desloratadine 5 mg (n = 140) or placebo (n = 92) and exposed to ragweed pollen on two consecutive days (7 h and 6 h). Symptoms were self-rated every 30 min. On both days, levocetirizine produced a greater improvement in the major symptom complex score (primary efficacy variable) than desloratadine (p = 0.015); both were better than placebo (p < 0.001). Levocetirizine acted earlier (1 h vs. 3 h) and produced greater symptom relief at 24 h than desloratadine (p = 0.003). Levocetirizine also alleviated nasal obstruction better than desloratadine (p = 0.007) on day 1; and better than placebo (p = 0.014) after the second dose on day 2, which was not observed with desloratadine. Levocetirizine and desloratadine were safe and well tolerated.

A new histamine measurement system employing a confocal laser microscope and cultured human dermal microvascular endothelial cells

BACKGROUND

Histamine causes the endothelial cells of blood vessels to contract. H(1) receptor antagonists block histamine from binding to the H(1) receptor, suppressing edema. But it is unknown whether they bring about similar effects in microvascular endothelial cells in the human skin.

OBJECTIVE

We devised a series of experiments to measure changes in Ca(2+) concentration within human dermal microvascular endothelial cells stimulated with histamine using a confocal laser microscope. Within a distinct concentration range, the observed changes in Ca(2+) concentration were proportional to the amount of histamine administered, raising the possibility that trace amounts of histamine and the amount of histamine binding to H(1) receptors could be quantified.

METHODS

An experiment was conducted in which the H(1) receptor-antagonistic actions of eight antihistamines and anti-allergy drugs with antihistamine properties were quantitatively evaluated using a system for performing the above quantification. Each evaluated drug was preloaded within the range 10(-9)-10(-3) M, histamine 10(-6) M was added, and changes in the intracellular concentration of Ca(2+) were noted so as to evaluate the drugs' antagonism of the H(1) receptor.

RESULTS

Within the measurable range of the system, epinastine was the most effective of the drugs tested in inhibiting changes in Ca(2+) concentration in cells stimulated with histamine.

CONCLUSION

Our system can be used to quantitatively measure and compare the actions of H(1) receptor antagonists on dermal microvascular endothelial cells, providing valuable information for dermatologists.

Emerging safety issues regarding long-term usage of H(1)receptor antagonists

The second generation histamine H(1)-receptor antagonists are important therapeutic tools in the treatment of atopic disease and may also have a place as an adjunct therapy for those patients whose allergic asthma coexists with allergic rhinitis. They are amongst the most widely prescribed and safest drugs in the world. However, as second generation H(1)-receptor antagonists are used to treat non-life threatening conditions, the risk of adverse effects is of vital importance. For many, the potential for sedation by some of the newer antihistamines still remains an issue, while there have recently been widespread concerns regarding the potential for cardiotoxicity and the impact of drug-drug interactions associated with some second generation H(1)-receptor antagonists. Consequently, progress with this class of drugs should involve not only increased efficacy but also improvements in their safety and specificity. Moreover, there is a trend towards using second generation H(1)-receptor antagonists as long-term therapy rather than confining their use to treating the short-term manifestations of allergic disease. To this end, a number of novel, potent and safe antihistamines have been developed which are either metabolites of active drugs or enantiomers. This review will examine some of the safety issues associated with established and newer second generation drugs particularly in relation to their long-term usage in adults and children.