Comparative inhibition profiles of three non-sedating antihistamines assessed by an extended Lewis model

Antihistaminic drugs are widely prescribed across a multitude of medical specialties such as Allergy and Dermatology. The potentially serious sedative effect of these valuable agents has previously restricted their full use and the choice of drug has been dictated more by individual patient acceptability than by any laboratory demonstrations of comparative efficacy. Unsurprisingly therefore, there is a trend towards prescribing those newer preparations which leave the central nervous system unclouded. We have studied the most frequently prescribed non-sedating antihistamine preparations, terfenadine (Triludan, Triludan Forte), cetirizine (Zirtek) and loratadine (Clarityn) in pharmacodynamic and relative efficacy trials using a quantifiable and reproducible extension of the classic Lewis model. The results indicate that two preparations, terfenadine 120 mg (Triludan Forte) and cetirizine 10 mg (Zirtek) are superior to their immediate rivals in degree of efficacy and/or speed of action. These results should assist clinicians in the positioning of effective, rapidly acting antihistamines for the symptomatic treatment of immediate hypersensitivity reactions such as urticaria and rhinitis.