Non drowsy antihistamine
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Non-Drowsy Antihistamines: Efficacy and Safety
Introduction to Non-Drowsy Antihistamines
Non-drowsy antihistamines, also known as second-generation antihistamines, are designed to treat allergic conditions without causing significant sedation. Unlike first-generation antihistamines, which readily cross the blood-brain barrier and induce drowsiness, second-generation antihistamines are formulated to minimize central nervous system (CNS) effects.
Mechanism of Action and Blood-Brain Barrier Permeability
Selectivity and CNS Effects
First-generation antihistamines, such as diphenhydramine and chlorpheniramine, are known to cross the blood-brain barrier, leading to sedation and impaired cognitive and psychomotor performance2 6. This sedative effect is primarily due to the blockade of central histaminergic receptors, along with potential interactions with serotonergic, cholinergic, and alpha-adrenergic receptors2.
In contrast, second-generation antihistamines, including loratadine, cetirizine, and fexofenadine, are large, lipophobic molecules with charged side chains that limit their ability to penetrate the blood-brain barrier2 4. This reduced permeability is a key factor in their non-sedating properties.
Clinical Efficacy and Safety
Comparative Sedative Effects
Studies have shown that second-generation antihistamines, such as loratadine and fexofenadine, have a sedative profile comparable to placebo, making them suitable for patients who need to avoid drowsiness3 6. For instance, loratadine has been demonstrated to have no significant effects on CNS functioning, including driving performance and cognitive tasks, in both self-report and physiological studies6.
Performance and Psychomotor Effects
Clinical trials have consistently shown that second-generation antihistamines do not impair psychomotor reflexes or driving performance, unlike their first-generation counterparts2 4. This makes them a safer option for individuals who need to maintain high levels of alertness and cognitive function.
Specific Non-Drowsy Antihistamines
Loratadine and Fexofenadine
Loratadine and fexofenadine are among the most commonly used non-drowsy antihistamines. Both drugs have been shown to be effective in treating allergic rhinitis and chronic urticaria without causing significant sedation4 6. Fexofenadine, in particular, is classified as a "non-brain-penetrating antihistamine," which further underscores its minimal CNS effects5.
Bilastine
Bilastine is another non-drowsy antihistamine that has been highlighted for its potent binding affinity to the H1 receptor and long-lasting action. Studies have shown that bilastine does not affect psychomotor or driving performance, even at higher doses, making it a reliable option for first-line therapy in mild allergic rhinitis5.
Conclusion
Non-drowsy antihistamines represent a significant advancement in the treatment of allergic conditions, offering effective symptom relief without the sedative side effects associated with first-generation antihistamines. Drugs like loratadine, fexofenadine, and bilastine provide safe and effective options for patients who need to maintain cognitive and psychomotor performance while managing their allergies.
Sources and full results
Most relevant research papers on this topic
Induction of prolonged, continuous slow‐wave sleep by blocking cerebral H1 histamine receptors in rats
Modern antihistamines, which are more selective for H1 histamine receptors, can induce prolonged, continuous slow-wave sleep in rats, highlighting their central role in histaminergic sleep regulation.
Non-RCT
Animal StudyPerformance effects of antihistamines.
Antihistamines can cause performance decrements, especially with first-generation agents, but newer, nonsedating, second-generation agents show no more sedation than placebo.
Comparative analysis of the sedative effects of mequitazine and other antihistaminic drugs : Review of the literature
Mequitazine has a low sedative profile, similar to cetirizine and loratadine, and differs from truly sedative antihistamines like dexchlorpheniramine, which cause drowsiness and fatigue in patients with atopy.
Systematic ReviewNonsedating antihistamines: pharmacology, clinical efficacy and adverse effects.
Nonsedating antihistamines, such as terfenadine and astemizole, are as effective as classic antihistamines without causing central nervous system or anticholinergic side effects.
Antihistamines for Allergic Rhinitis Treatment from the Viewpoint of Nonsedative Properties
Non-brain-penetrating antihistamines, such as fexofenadine and bilastine, are recommended for first-line therapy of mild allergic rhinitis due to their nonsedative properties.
Literature Review
Highly CitedLoratadine: a non‐sedating antihistamine. Review of its effects on cognition, psychomotor performance, mood and sedation
Loratadine, a second-generation H1-receptor antagonist, has comparable effects on somnolence, fatigue, and mood without sedating the central nervous system, compared to diphenhydramine, a common first-generation antihistamine.
Literature ReviewHighly CitedVariations among non-sedating antihistamines: are there real differences?
Non-sedating antihistamines can cause mild to moderate sedation, but their safety margin is narrow enough to avoid serious side effects.
A comparison between astemizole and other antihistamines on sleep-wakefulness cycles in dogs
Astemizole has no significant effect on sleep-wakefulness patterns in dogs, suggesting it may lack common side-effects of antihistamines like sedation and dryness of mucosal surfaces.
Non-RCTAnimal StudyNon-sedating antihistamines.
Non-sedating antihistamines, such as terfenadine and astemizole, are effective for treating histamine-mediated conditions without causing drowsiness or anticholinergic side effects.
The effectiveness of the nonsedating antihistamine loratadine plus pseudoephedrine in the symptomatic management of the common cold.
The non-sedating antihistamine loratadine and pseudoephedrine combination effectively relieves common cold symptoms, with potential side effects of dry mouth, insomnia, and nervousness.
RCT