![]() Therefore, most of the studies were conducted investigating levocetirizine, without demonstrating a superiority, nor in efficacy or in safety, of the enantiomer compared to the racemic compund. However, at the beginning of the twenty-first century, levocetirizine was commercialized worldwide for a patent reason. In these years, cetirizine was the most relevant compound in its class and is still very popular. Ĭetirizine is a second-generation antihistamine and was launched in the Italian market in 1989, such as 30 years ago. Some second-generation drugs have also some important anti-inflammatory and anti-allergic effects that occur by a decrease in : 1) production of cytokines by proinflammatory drugs and in the release of other mediators by mastocytes and basophils 2) recruitment of eosinophils in the late phase of allergic reactions 3) expression of membrane receptors in nasal epithelial cells and the vascular endothelium, particularly the leukocyte Intercellular Adhesion Molecule 1 (ICAM-1), which favours leukocyte migration from the blood to the respiratory mucosa and constitutes the main receptor for respiratory viruses to which the untreated atopic subject appears to be more susceptible. It is possible to distinguish first and second-generation antihistamines pharmacological effects and therapeutic applications are similar, but second-generation antihistamines have fewer adverse effects because they are more selective for peripheral H1 receptors. ![]() H1-antihistamines are widely used in patients to treat symptoms that are secondary to histamine release, which is typical of certain allergic conditions. The action of histamine on H4 receptors induces chemotaxis, cytokine secretion, and upregulation of adhesion molecules. H4 receptors are found on cells of the immune system, in the gastrointestinal tract, in the CNS, and on afferent neurons with primary sensors. H3 receptors are mainly expressed in the CNS and act as an autoreceptor on histaminergic neurons, inhibiting the release of histamine and modulating that of other neurotransmitters. Additionally, histamine stimulates gastric acid secretion via H2 receptors. By acting on H1, histamine causes itching, stimulates secretion from the nasal mucosa, contracts smooth muscle in the bronchi and intestines, and relaxes smooth muscle in small blood vessels. H1 and H2 receptors are distributed in both the peripheral and the central nervous system (CNS) and allow histamine to exert effects on smooth muscles and glands. Histamine can act on four types of receptors: H1, H2, H3, and H4. The concentration of histamine is particularly high in mast cells, that reside in the respiratory tree, gastrointestinal tract, and skin. To conclude, it is important to understand that Zyrtec may make you sleepy, but effects vary by individual.Histamine is the pivotal mediator of an allergic reaction. skin reaction to an allergen producing hives, swelling and inflammation). Many studies put Zyrtec as the most effective second-generation antihistamine for the treatment of wheal and flare reactions (i.e. ![]() In those taking Zyrtec at the 10 mg dose, the incidence rate increased to 14%.Īlthough Zyrtec is associated with higher rates of drowsiness than other second-generation antihistamines, it may be the most effective medication for certain types of allergies. For example, the incidence of drowsiness was 11% in those taking Zyrtec 5 mg. More specifically, clinical trial data for Zyrtec indicated the following incidence rates for drowsiness and related effects:įatigue and drowsiness are dose-related, meaning higher doses are more likely to cause side effects. The actual incidence of drowsiness among individuals taking Zyrtec isn't fully known but is reported to be around 5-15%. Most studies find that Zyrtec causes sedation at a much higher rate than other second-generation antihistamines. For this reason, it is not marketed as "non-drowsy" as other products such as Claritin and Allegra are. Unfortunately, Zyrtec (cetirizine) is the only second-generation antihistamine that is known to cause significant sedation in individuals. Second-generation antihistamines offer significant benefit over first generation antihistamines, such as Benadryl in that they last about 24 hours per dose and are typically non-drowsy. There are currently four second-generation antihistamines available over the counter (OTC) in the United States: Zyrtec (cetirizine) is classified as a "second-generation" antihistamine. Below, we discuss Zyrtec in detail as well as the incidence of sedative side effects. Yes, Zyrtec (cetirizine) can cause you to feel sleepy and can create a general feeling of drowsiness and sedation.
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