Third-generation antihistamines are defined as being metabolites or enantiomers of previously available drugs and can therefore lead to an increase in efficacy and/or safety. In Canada these include: fexofenadine and desloratidine .
What is the advantage of second generation antihistamines?
Second-generation antihistamines offer several advantages over classic H1 antihistamines, including lack of sedation and impairment of performance, longer duration of action, and absence of anticholinergic side effects.
What is second generation antihistamines?
The second-generation oral antihistamines currently available in the United States are cetirizine, levocetirizine, desloratadine, fexofenadine, and loratadine. A limited number of studies comparing these agents suggest no major differences in efficacy. Only cetirizine causes drowsiness more frequently than placebo.
What are characteristics of 2nd generation antihistamine?
The newer, second-generation H1-antihistamines are far more selective for peripheral histamine H1-receptors and have a better tolerability profile compared to the first-generation agents. The most common adverse effects noted for second-generation agents include drowsiness, fatigue, headache, nausea and dry mouth.
Does Zyrtec cross the blood brain barrier?
Derived from the first-generation antihistamine hydroxyzine, cetirizine does not cross the blood-brain barrier to the extent of its first-generation counterparts; as a result, cetirizine is an effective treatment of allergic rhinitis that simultaneously minimizes the possibility of adverse sedative effects.
When should you not take antihistamines?
closed angle glaucoma. high blood pressure. stenosing peptic ulcer. blockage of the urinary bladder.
What is the difference between 1st generation and 2nd generation antihistamines?
First-generation antihistamines block both histaminic and muscarinic receptors as well as passing the blood-brain barrier. Second-generation antihistamines mainly block histaminic receptors and do not pass the blood-brain barrier.
Is Zyrtec a first or second generation antihistamine?
Second-generation OTC antihistamines Loratadine (brand names include Alavert, Claritin) Cetirizine (brand names include Zyrtec)
Can you take 2 types of antihistamines?
Don’t take two different types of antihistamines simultaneously. Don’t take more than the recommended dosage. Don’t double up on doses.