Bilastine vs. hydroxyzine: occupation of brain histamine H1-receptors evaluated by positron emission tomography in healthy volunteers

AimA close correlation exists between positron emission tomography (PET)-determined histamine H-1-receptor occupancy (H1RO) and the incidence of sedation. Antihistamines with H1RO <20% are classified as non-sedating. The objective was to compare the H1RO of bilastine, a second generation antihistamine, with that of hydroxyzine. MethodsThis randomized, double-blind, crossover study used PET imaging with [C-11]-doxepin to evaluate H1RO in 12 healthy males (mean age 26.2 years), after single oral administration of bilastine (20mg), hydroxyzine (25mg) or placebo. Binding potentials and H1ROs were calculated in five cerebral cortex regions of interest: frontal, occipital, parietal, temporal, insula. Plasma bilastine concentrations, subjective sedation (visual analogue scale), objective psychomotor performance (digital symbol substitution test), physiological variables and safety (adverse events, AEs), were also evaluated. ResultsThe mean binding potential of all five regions of interest (total binding potential) was significantly greater with bilastine than hydroxyzine (mean value 0.26 vs. 0.13, P<0.01; mean difference and 95% CI -0.130 [-0.155, 0.105]). There was no significant difference between bilastine and placebo. Overall H1RO by bilastine was significantly lower than that by hydroxyzine (mean value -3.92% vs. 53.95%, P<0.01; mean difference and 95% CI 57.870% [42.664%, 73.075%]). There was no significant linear relationship between individual bilastine plasma concentrations and total binding potential values. No significant between-treatment differences were observed for sedation and psychomotor performance. Twenty-six non-serious AEs were reported. Sleepiness or sedation was not reported with bilastine but appeared in some subjects with hydroxyzine. ConclusionsA single oral dose of bilastine 20mg had minimal H1RO, was not associated with subjective sedation or objective impairment of psychomotor performance and was devoid of treatment-related sedative AEs, thus satisfying relevant subjective, objective and PET criteria as a non-sedating antihistamine.