TL;DR: Cetirizine 10 mg/day appears to be as effective as conventional dosages of other established antihistamines such as astemizole, hydroxyZine, ketotifen, loratadine or terfenadine in relieving symptoms of these disorders, and is associated with a significantly lower incidence of sedation than hydroxyzine.
Abstract: Cetirizine, the carboxylated metabolite of hydroxyzine, is a specific and long-acting histamine H1-receptor antagonist. It has marked antiallergic properties and inhibits eosinophil chemotaxis during the allergic response. Clinical trial results indicate that cetirizine is an effective and well tolerated treatment for seasonal/perennial allergic rhinitis and chronic idiopathic urticaria in adults, and for seasonal/perennial allergic rhinitis in children. Cetirizine 10 mg/day appears to be as effective as conventional dosages of other established antihistamines such as astemizole, hydroxyzine, ketotifen, loratadine or terfenadine in relieving symptoms of these disorders, and is associated with a significantly lower incidence of sedation than hydroxyzine. However, when sedation was subjectively assessed, cetirizine appeared to be more sedating than placebo, loratadine or terfenadine in some clinical trials. This difference was not observed in several other double-blind studies. In contrast, when assessed objectively in pharmacodynamic comparisons, cetirizine was rarely more sedating than placebo or other second generation histamine H1-receptor antagonists. Cetirizine may also have a role in the treatment of certain forms of physical urticaria, atopic dermatitis and reactions to mosquito bites. In addition, it is being studied for the treatment of allergic asthma in adults and children. The pharmacokinetic profile and predominantly renal excretion of cetirizine suggest that this agent may have a reduced potential for adverse drug interactions involving hepatic enzyme systems compared with other histamine H1-receptor antagonists which are extensively metabolised. Thus, cetirizine, with its rapid onset and long duration of action, appears to provide a useful alternative to the antihistamine agents in clinical use.
TL;DR: A double-blind study of 537 patients evaluated the relative efficacy of four drugs used in treating alcohol withdrawal symptoms, specifically to prevent delirium tremens and convulsions, concluding that chlordiazepoxide appears to be the drug of choice among those tested.
Abstract: A double-blind study of 537 patients evaluated the relative efficacy of four drugs—chlordiazepoxide, chlorpromazine, hydroxyzine, and thiamine—commonly used in treating alcohol withdrawal symptoms, specifically to prevent delirium tremens and convulsions. Of the 55 patients who developed these symptoms, two percent were in the chlordiazepoxide group; the incidence ranged from ten to 16 percent in the other treatment groups. The authors conclude that chlordiazepoxide appears to be the drug of choice among those tested.
TL;DR: Loratadine, with its attributes of once daily administration, fast onset of action and essentially nonsedating properties, would appear to be an appropriate first-line agent for the treatment of allergic rhinitis or urticaria.
Abstract: Loratadine is a long-acting antihistamine agent, exhibiting partial selectivity for peripheral histamine H1-receptors. To date, loratadine has been evaluated in allergic rhinitis, urticaria and, to a limited extent, in asthma. In several large controlled comparative clinical studies, loratadine was superior to placebo, faster acting than astemizole and as effective as azatadine, cetirizine, chlorpheniramine (chlorphenamine), clemastine, hydroxyzine, mequitazine and terfenadine in patients with allergic rhinitis and chronic urticaria. The clinical effectiveness of loratadine in asthma is at present unclear. Loratadine is well tolerated. At dosages of 10 mg daily, commonly reported adverse events were somnolence, fatigue and headache. Sedation occurred less frequently with loratadine than with azatadine, cetirizine, chlorpheniramine, clemastine and mequitazine. Serious ventricular arrhythmias, as reported with some other second generation histamine H1-receptor antagonists, have not been observed with loratadine to date. Thus, loratadine, with its attributes of once daily administration, fast onset of action and essentially nonsedating properties, would appear to be an appropriate first-line agent for the treatment of allergic rhinitis or urticaria.
TL;DR: Hydroxyzine is a useful drug for the symptomatic treatment of interstitial cystitis, especially in patients with documented allergies and/or evidence of bladder mast cell activation.
TL;DR: Results from controlled clinical trials indicate that cetirizine is an effective and well tolerated treatment of seasonal and perennial allergic rhinitis and chronic idiopathic urticaria, and it appears to provide a useful alternative to other 'nonsedating' antihistamines.
Abstract: Cetirizine, a piperazine derivative and carboxylated metabolite of hydroxyzine, is a potent histamine H1-receptor antagonist with antiallergic properties. It has marked affinity for peripheral histamine H1-receptors and, at the standard dose of 10mg daily, lacks the CNS depressant effects of standard antihistamines. In addition, it inhibits histamine release and eosinophil chemotaxis during the secondary phase of the allergic response. Results from controlled clinical trials indicate that cetirizine is an effective and well tolerated treatment of seasonal and perennial allergic rhinitis and chronic idiopathic urticaria. Cetirizine appears to be as effective as conventional dosages of terfenadine, chlorpheniramine and hydroxyzine in relieving symptoms associated with these disorders and produces a markedly lower incidence of sedation than chlorpheniramine, hydroxyzine and several other standard antihistamines. Thus, cetirizine appears to provide a useful alternative to other 'nonsedating' antihistamines; cetirizine may also have a future role in the treatment of allergic asthma and certain forms of physical urticaria.