SELECTED ARTICLES FROM THE RECENT LITERATURE 2004

8/17/04

Cetirizine vs. desloratadine - comparative antihistamine effects

Summary
Background - There is considerable promotion/advertising of the more recent antihistamines (AH) with claims that a particular drug is "most effective" in combating histamine effects in allergies. The degree of inhibition of histamine-induced skin whealing has been a common way of assessing the AH potency of individual drugs.

Findings - Purohit et al of the University Hospital in Strasbourg, France compared the effects of pre-treatment with single doses of cetirizine (Cet) and desloratadine (Desl) on skin whealing responses to histamine prick tests (100 mg/mL) in 18 healthy adults. A double blind, randomized, placebo controlled protocol was used. The authors found that pre-treatment with either Cet or Desl inhibited whealing responses significantly more than did placebo (p<0.001). However, Cet pre-treatment was significantly more inhibitory than was Desl pre-treatment (p<0.001). For example, histamine-induced whealing was inhibited ä 70% at 0.3 - 3 hours in all following pre-treatment with Cet but in only 16% of the Desl pre-treated subjects. The duration of inhibition of whealing responses was also much longer following Cet pre-treatment (median duration 21 hours) than Desl pre-treatment (< 3 hours).

Reference
Ann Allergy, Asthma, Immunol 2004;92:635-40

Editor's Comments
These findings were not surprising to me. Most previous studies have shown that Cet had significantly more potent and long-lasting inhibitory effects on histamine-induced skin whealing than did loratadine (Claritin) the parent drug of Desl. Although Desl (Clarinex) may be somewhat more potent than Claritin, I believe that it is not in the same level of AH activity as is Cet.

However, it is still unclear how well the inhibitory effect of an AH agent on histamine-induced skin whealing predicts therapeutic effects of that AH on allergic respiratory diseases. More investigation is warranted.

 

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