Suppressive effects of histamine skin reactivity by a nonsedating antihistamine-mequitazine.

The suppressive activity of mequltazlne (Mal) on histamine skin reactivity was evaluated In 29 healthy subjects (age 22·25 years) in a slngl.bllnd study. Fifteen subjects received MOZ, at a dosage of 5 mg BID, for 7 days while 14 served as controls. A prick skin test with saline or histamine hydrochloride (1 mglml and 10 mglml) was performed in duplicate, on both forearms, starting from the baseline day and continuing for 4 days after medication had been discontinued (total of 11 days). The skln·test subject and the reader was unaware of the reno domlzation process. Mean diameters of wheal and flare as well as the skin Index scores (after Voorhost) were used in the analysis. Maximal flare suppression (as compared to the baseline values) was observed on day 6 (97% suppression for 1 mglml and 54% suppression for 10 mglml, p < 0.01). Suppression of wheal size was significant (19% for 1 mglml and 28% for 10 mg/ml) but was not clinically relevant. Suppression of skin Index scores was maximal on day 6 (71% for 1 mglml and 43% for 10 mglml, p <0.01). After MOZ had been discontinued, all measurements gra· dually returned to baseline values and were not different therefrom within 3 days. However, final measurements of wheal and flare were smaller than baseline values (60-94% of baselines). We conclude that Mal, at the manufacturers's recommended dose of 5 mg BID, significantly suppressed flare size of histamine skin tests and recommend that MOZ be discontinued for at least 3 days prior to performing allergy skin tests.