Sedating antihistamines over the counter
"We're not saying that there's not a difference," says lead researcher Bruce G.
Bender, Ph D, of National Jewish Medical and Research Center in Denver.
Another advantage of the newer antihistamines is that they're available in time-release versions.
That means you can control your symptoms with only 1 or 2 doses each day compared with older medications, which usually require doses every 4 to 6 hours to maintain their effectiveness.
Histamine release in the brain triggers secondary release of excitatory neurotransmitters such as glutamate and acetylcholine via stimulation of H Research into these drugs led to the discovery that they were H1 antagonists and also to the development of H2 antagonists, where H1 antihistamines affected the nose and the H2 antihistamines affected the stomach.Antihistamines that target the histamine H receptors in the upper gastrointestinal tract, primarily in the stomach.Histamine receptors exhibit constitutive activity, so antihistamines can function as either a neutral receptor antagonist or an inverse agonist at histamine receptor.Histamine produces increased vascular permeability, causing fluid to escape from capillaries into tissues, which leads to the classic symptoms of an allergic reaction — a runny nose and watery eyes. Antihistamines suppress the histamine-induced wheal response (swelling) and flare response (vasodilation) by blocking the binding of histamine to its receptors or reducing histamine receptor activity on nerves, vascular smooth muscle, glandular cells, endothelium, and mast cells.
Itching, sneezing, and inflammatory responses are suppressed by antihistamines that act on H1-receptors.Some second-generation antihistamines, notably cetirizine, can interact with CNS psychoactive drugs such as bupropion and benzodiazepines.-antihistamines are among first-line therapy to treat gastrointestinal conditions including peptic ulcers and gastroesophageal reflux disease. Most side effects are due to cross-reactivity with unintended receptors.