Histamine 1 antagonists

Antihistamines for allergic rhinitis

Antihistamines counteract acute symptoms of allergic rhinitis by antagonizing the histamine receptor. Since the effects of allergic rhinitis are predominantly mediated via the h1-receptor, h1-receptor antagonists are therefore useful in the treatment.Most widely used antihistamines for allergic rhinitis are cetirizine, loratadine, desloratadine, levocabastine, and azelastine.

Antihistamines can be administered as nasal spray or as tablets. However, some patients complain of increased symptoms after local application. This is due to the rebound effect from topically applied drugs. The tablets are prescribed when more organs are involved (eyes, skin).

Unlike the first-generation antihistamines, the second-generation antihistamines are less sedating. Other side effects include central actions such as dizziness and mild GI effects like nausea and loss of appetite.


Every springtime, a young healthy man is bothered by episodes of nasal congestion accompanied by sneezing and watery eyes. He has no cough. PE: afebrile, swelling of his nasal passageways. His problems are most likely produced by release of chemical mediators from which of the following cell types?


The antihistamine with the most pronounced sedative properties is