This sedating activity is sometimes used in managing conditions such as eczema where sleep maybe disturbed due to pruritus.Sedating antihistamines also have significant antimuscarinic activity and should be used with caution in patients with prostatic hypertrophy, urinary retention and angle-closure glaucoma.The difference between them is really blurred." "Under some circumstances, the nonsedating formulas do cause sedation and in some cases, these sedating formulas do not," he tells Web MD."In some studies we reviewed, some people actually experienced more sedation with the newer, nonsedating formulas than with the older, sedating products.Additional administration of epinephrine, often in the form of an autoinjector (Epi-pen), is required by people with such hypersensitivities.H-antihistamines can be administered topically (through the skin, nose, or eyes) or systemically, based on the nature of the allergic condition.
First-generation antihistamines include diphenhydramine (Benadryl), carbinoxamine (Clistin), clemastine (Tavist), chlorpheniramine (Chlor-Trimeton), and brompheniramine (Dimetane).Antihistamines are classified into two groups – the first-generation (“sedating”) and second-generation (“non-sedating”).Sedating antihistamines cause sedation as they are highly lipid soluble and readily cross the blood brain barrier. Agents where the main therapeutic effect is mediated by negative modulation of histamine receptors are termed antihistamines; other agents may have antihistaminergic action but are not true antihistamines.In common use, the term "antihistamine" refers only to H In type I hypersensitivity allergic reactions, an allergen (a type of antigen) interacts with and cross-links surface Ig E antibodies on mast cells and basophils.The drugs of the first antihistamine generation are: promethazine, alimemazine, dexchlorpheniramine, brompheniramine, buclizine, carbinoxamine and doxylamine, are sedating and elicit a drowsiness which can be awkward.