Mechanism of action of sedating antihistamines
156 papers were found using the reported searches, of which 4 presented the best evidence to answer the clinical question.The author, date and country of publication, patient group studied, study type, relevant outcomes, results and study weaknesses of these best papers are tabulated.
Once released, the histamine can react with local or widespread tissues through histamine receptors.The cookies contain no personally identifiable information and have no effect once you leave the Medscape site.receptor sites, responsible for immediate hypersensitivity reactions such as sneezing and itching.Several of the older drugs, called first-generation antihistamines, bind non-selectively to H receptors in the central nervous system as well as to peripheral receptors, and can produce sedation, inhibition of nausea and vomiting, and reduction of motion sickness.The second-generation antihistamines bind only to peripheral HThe first-generation antihistamines may be divided into several chemical classes.Many of the first-generation agents, especially those of the ethanolamine and ethylenediamine subgroups, have significant atropine-like effects on peripheral muscarinic receptors.
This action may be responsible for some of the (uncertain) benefits reported for nonallergic rhinorrhea but may also cause urinary retention and blurred vision. This drug is promoted as an antiserotonin agent and is discussed with that drug group.
Diphenhydramine and promethazine are actually more potent than procaine as local anesthetics.
They are occasionally used to produce local anesthesia in patients allergic to conventional local anesthetic drugs.
The authors of the American College of Chest Physicians Updates on Cough Guidelines (2006) recommend that, for cough associated with the common cold, first-generation antihistamine-decongestants are more effective than newer, non-sedating antihistamines.
First-generation antihistamines include diphenhydramine (Benadryl), carbinoxamine (Clistin), clemastine (Tavist), chlorpheniramine (Chlor-Trimeton), and brompheniramine (Dimetane).
Members of this class of drugs may also be used for their side effects, including sedation and antiemesis (prevention of nausea and vomiting). They have no effect on rate of histamine release, nor do they inactivate histamine.