Facial thermography is a sensitive tool to determine antihistaminic activity: comparison of levocetirizine and fexofenadine

Aims To assess the antihistaminic activity of levocetirizine and fexofenadine 2 h and 24 h after drug administration using facial thermography and to compare the results with those using well-established parameters of antihistaminic activity in the nose and skin. Methods This was a randomized, double-blind, three-treatment, three-period, single-dose, cross-over study in healthy males taking levocetirizine 5 mg, fexofenadine 120 mg or placebo. The primary endpoint was nasal skin temperature after nasal histamine challenge recorded for 20 min at 2 and 24 h after drug intake. The secondary endpoints were nasal symptoms and a histamine skin prick test. Results Thirty subjects were randomized. At 2 h after drug intake the inhibition of the nasal temperature increase from baseline was not significantly different between levocetirizine and fexofenadine. At 24 h it was significantly more pronounced after levocetirizine than fexofenadine (difference: least-squares mean: -0.13 degrees C; P <= 0.024, 95% CI -0.24, -0.02). Both drugs significantly reduced (P <= 0.001) the mean temperature increase from baseline compared with placebo at 2 and 24 h (least-squares mean increase and (95% CI): levocetirizine, -0.28 degrees C (-0.42, -0.14) and -0.32 degrees C (-0.43, -0.21); fexofenadine -0.35 degrees C (-0.49, -0.21) and -0.19 degrees C (-0.30, -0.08), respectively). Results of nasal symptom score and wheal and flare were consistent with the thermography results. Conclusions Facial thermography is an objective, non-invasive and sensitive method to study antihistaminic activity at the nose level. Levocetirizine and fexofenadine demonstrate the same activity at 2 h after drug intake, but levocetirizine has a more sustained activity at 24 h.