Assessment of the anticholinergic effect of the new antihistamine mizolastine in healthy subjects

1. Twelve healthy subjects were enrolled in a double-blind placebo controlled cross-over study in order to assess the possible anticholinergic effects of four doses of a new antihistamine compound, mizolastine, compared with hyoscine butylbromide (HBB) used as a reference anticholinergic drug. 2. Although mizolastine, a potent and selective H1-receptor blocker has no affinity for muscarinic receptors and does not antagonize the effects of carbachol in rodents, a study was initiated to investigate its effects on various effectors possessing muscarinic receptors (eye, heart, sweat gland, salivary gland). 3. HBB (40 mg, s.c.) impaired accommodation, decreased salivary flow and inhibited cardiac sinus arrhythmia. Pupil diameter and maximum constriction speed, carbachol-induced skin sweating and Valsalva ratio were unaffected. 4. Mizolastine (5, 10, 20, 40 mg p.o.) did not affect any parameter at any time point, demonstrating a lack of anticholinergic effect.