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.The newer antihistamines are available only by prescription.Some do not appear to produce clinically significant sedation at usual doses, while others have a low rate of sedation.All are efficacious in controlling symptoms of allergic rhinitis (ie, sneezing, rhinorrhea, itching) but do not significantly improve nasal congestion.Sold over the counter (OTC), they are less expensive than prescription nonsedating antihistamines. Nonsedating antihistamines, also called new, or second-generation antihistamines, are just as effective against nasal allergy symptoms as older medications. They make you less sleepy and groggy, and are less likely to cause problems with increased eye pressure, which may worsen glaucoma symptoms.Another advantage of the newer antihistamines is that they're available in time-release versions.The original, first generation antihistamines have drawbacks that include being short-acting, making it difficult to concentrate, and drowsiness.The major side effect of this allergy medication is drowsiness.
They compete with histamine for histamine receptor type 1 (H1) receptor sites in the blood vessels, GI tract, and respiratory tract, which, in turn, inhibits physiologic effects that histamine normally induces at the H1 receptor sites.
The author, date and country of publication, patient group studied, study type, relevant outcomes, results and study weaknesses of these best papers are tabulated.
It is concluded that there is no good evidence for the use of non-sedating antihistamines in the common cold.
We attempt to clarify the differences among these drugs by providing side-by-side comparisons of some of the best antihistamines available (below). Simply put, it is a medication that relieves allergy symptoms by blocking histamine, the chemical “culprit” that causes many symptoms.
Antihistamines are classified as H1 blockers and H2 blockers, depending on the type of receptors (on the surface of cells) that they act on.