Cetirizine

Antihistamines are drags used to counteract the effects of histamine on body organs and structures. Examples of antihistamines include diphenhydramine (Benadryl), loratadine (Claritin), fexofenadine (Allegra), and cetirizine (Zyrtec). A new antihistamine, deslorata-dine (Clarinex), is die active metabolite of loratadine and is intended to eventually replace loratadine (Claritin). Topical corticosteroid nasal sprays such as fluticasone propionate (Flonase) or triamcinolone ace-tonide (Nasacort AQ) are also used for nasal allergy symptoms. See Chapter 56 for more information on die topical corticosteroids. 

The belief that histamine (HT) has a central effect stems from the knowledge that all the classical antihistamines (Hi receptor antagonists) used to treat allergic reaction, such as hay fever, caused marked sedation if, like mepyramine and promethazine, they can cross the blood-brain barrier, but fail to do so if, like terfenedine and cetirizine, they do not. 

Values are the means from six separate experiments. SE was less than 10% of the mean. Dose of test compounds, chlorpheniramine maleate and cetirizine are 10 mg/kg for antihistaminic activity, and 5 mg/kg for sedative-hypnotic activity... 

As sedation is one of the major side effects associated with antihistamines, the test compounds were also evaluated for their sedative potentials. This was determined by measuring the reduction in locomotor activity using an ac-tophotometer [6,7]. The test compounds and the reference standards (chlorpheniramine maleate and cetirizine) were administrated orally at a dose of 5 mg/kg in 1% CMC. 

Cetirizine (Zyrtec) 10 mg orally daily Second-line agent for allergic rhinitis during second and third trimesters only. 

First-generation antihistamines are effective, but associated sedation and psychomotor impairment limit chronic use. Efficacy and safety of second-generation antihistamines in children have been demonstrated in clinical trials.33 Cetirizine is indicated for children 6 months of age and older, loratadine for children 2 years of age and older, and fexofenadine for children 6 years of age and older.15... 

Figure 3.4 Microspeciation of cetirizine, a three-pi molecule [142], The numeric quantities refer to micro-pKa values. The asterisks denote the principal species at various pH states. [Avdeef, A., Curr. Topics Med. Chem., 1, 277-351 (2001). Reproduced with permission from Bentham Science Publishers, Ltd.]... 

Multiwavelength spectrophotometric resolution of the micro-equilibria of cetirizine, Anal. Sri. 2001, 17, 1203-1208. 

Intranasal corticosteroids are the most effective treatment for allergic rhinitis during pregnancy. Beclomethasone and budesonide have been used most. Nasal cromolyn and first-generation antihistamines (chlorpheniramine, tripelennamine, and hydroxyzine) are also considered first-line therapy. Loratadine and cetirizine have not been as extensively studied. 

Phenomenex (see 2006 Catalog, SPE products) Strata-X Polar functionalized styrene-divinylbenzene polymer Reversed phase with weakly acidic, hydrogen bond donor, acceptor, and dipolar interactions Cetirizine (76) pyridoxine (77) omeprazole (78) mycophenolic acid (79) 25-hydroxy-vitamin D3 (80)... 

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