Knowra Second-generation antihistamine Second-generation antihistamine A drug that blocks histamine H1 receptors and is designed to relieve allergy symptoms while entering the brain less readily than first-generation antihistamines.
Histamine H1 receptor : A receptor through which histamine promotes allergic symptoms and other physiological responses. Second-generation drugs reduce allergy symptoms by blocking this receptor.
Allergic rhinitis : Inflammation of the nasal lining caused by an allergic response, often producing sneezing, itching, and congestion. Oral and nasal antihistamines can relieve its itching, sneezing, and runny nose.
First-generation antihistamine : An H1 antihistamine that readily enters the brain and often causes sedation and anticholinergic effects. These older drugs provide the clearest contrast in brain penetration and adverse effects.
Drug-induced somnolence : Excessive sleepiness caused or worsened by a medication. Some second-generation agents still cause sleepiness, particularly at higher doses.
Blood–brain barrier : A selective interface between blood and brain tissue that limits the passage of many substances into the central nervous system. Limited passage across this barrier is the design feature that reduces central effects.
Urticaria : A skin condition marked by transient, itchy raised welts, commonly called hives. H1 blockade is a standard treatment for the itching and welts.
Diphenhydramine : A first-generation H1 antihistamine used for allergies, itching, and motion sickness, with sedating effects. It exemplifies the sedation that motivated less brain-penetrant alternatives.
Driving under the influence of drugs : Operating a vehicle while impaired by a psychoactive substance or medication. Even modest drowsiness can impair driving, despite a drug's low-sedation reputation.
P-glycoprotein : A membrane transporter that exports many compounds from cells, including at the blood–brain barrier. Its efflux activity helps keep some antihistamines out of the brain.
Cetirizine : A second-generation H1 antihistamine used for allergic rhinitis and urticaria. It is a common option, though it can cause more drowsiness than some peers.
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