The efficacy of a multiple oral dose treatment with
mebhydroline (
Omeril coated
tablets, 100 mg t.i.d.) was examined in 3 studies which were performed in a randomized, double-blind and placebo-controlled 2-way cross-over design. A second target was to investigate the suitability of different pharmacodynamic models for testing the efficacy of
antihistamines. Study A involved a nasal provocation with a specific
allergen in 11 symptom-free patients suffering from
seasonal allergic rhinitis. In study B, a nasal provocation with
histamine was investigated in 11 healthy volunteers. Study C involved a cutaneous provocation with a specific
allergen in 12 symptom-free patients suffering from
seasonal allergic rhinitis/atopy. The
mebhydroline treatment's superiority over placebo was shown statistically at the 95% confidence level for the symptoms itchy nose in study A and for nasal congestion in study B. In study C,
allergen-induced weals (planimetric measurement) and
itching (visual analog scale) were significantly changed by
mebhydroline. A qualitative evaluation revealed a reaction intensity that differed between the 2 treatments to a clinically relevant degree, however, without reaching significance. On the basis of the data it is expected that the clinical efficacy of
mebhydroline may be further substantiated in confirmatory clinical trials which should include placebo and positive controls. The test methods used differed in their suitability for measuring the pharmacodynamic effects of
antihistamines. Overall, the most clear-cut results were seen in
hay fever patients using a specific
allergen for provocation. The planimetric assessment of weal response should be preferred as a cutaneous model. Both AR and AARM have their clinical relevance. Based on highly significant results of a subgroup analysis there are indications in favor to AR, but momentary there is no definite conclusion in favor of or against either of the 2 methods.