Evaluation of the sedative and some anticholinergic effects of the H1 antagonists loratadine and pheniramine in experimental animals

ABSTRACT

All antihistaminic drugs have adverse effect of some degree. The most common side effects are sedation and anticholinergic responses. On isolated rabbit jejunum pheniramine [1-2 ug/ml] reduced significantly contraction induced by a submaximal dose of acetylcholine. However, loratadine [1-16 ug/ml] produced no reduction. Loratadine in doses up to [300 mg/kg] which is more than 300 times the effective antihistaminic dose, produced no significant effect on spontaneous motor activity in motor coordination nor in parkinsonism induced by fluphenamine [10 mg/kg s.c] in adult rats. On the other hand, pheniraine [5 mg/kg] intraperitoneal reduced significantly spontaneous motor activity and motor coordination in experimental rats. Like loratadines, it has no effect on fluphenazine induced parkinsonism. It can be concluded that loratadine is a nonsedating antihistaminic with no peripheral or central anticholinergic effects even in doses 300 times the antihistaminic dose. So, it is a safe and well tolerate