Which agent is a nonsedating antihistamine
Antihistamines are inhibitors of histamine receptors. H1-antihistamines, inhibit competitively H1 receptors and the corresponding effects i. They do not inhibit antigen/antibodies reactions, nor histamine release, they inhibit H1 effects. H1-antihistamines have been used for more than fifty years in treating various allergic manifestations. H1-antihistamines which penetrate into brain elicit, by inhibiting stimulant effect of histamine, drowsiness.Ceterizine is a racemic; one of its isomers called levocetirizine is also released on the market.Mizolastine does not induce, in usual dosage, prolongation of QT interval; however its combination with macrolides and imidazol antifungal agents is disadvised because of a possible inhibition of its catabolism.The two first H1-antihistamines without sedating effect to be marketed were terfenadine and astemizole.
Common combination products containing antihistamines include Actifed, Allerest, Contac, Coricidin, Dimetapp, Dristan, Drixoral, Excedrin PM, Nyquil, Nytol, Pamprin, Pedia Care, Tavist, Triaminic, Triaminicol, Unisom Dual Relief Formula, and Vicks Pediatric Formula 44.
Terfenadine, in addition to its antihistamine effects, also acts as a potassium channel blocker (K Toxicity is possible after years of continued use with no previous problems as a result of an interaction with other medications such as erythromycin, or foods such as grapefruit.
The addition of, or a dosage increase in, these CYP3A4 inhibitors makes it harder for the body to metabolize and remove terfenadine.
In larger plasma concentrations, it may lead to toxic effects on the heart's rhythm (e.g. In June 1990, evidence of serious ventricular arrhythmias among those taking Seldane prompted the FDA to issue a report on the risk factors associated with concomitant use of the drug with macrolide antibiotics and ketoconazole. Food and Drug Administration (FDA) had earlier approved a generic version of Seldane made by IVAX Corporation of Miami, the FDA recommended terfenadine-containing drugs be removed from the market and physicians consider alternative medications for their patients.
and the issue attracted mass media attention in reports that people with liver disease or who took ketoconazole, an antifungal agent, or the antibiotic erythromycin, could suffer cardiac arrhythmia if they also took Seldane. Seldane (and Seldane-D, terfenadine combined with the decongestant pseudoephedrine) were removed from the U. market by their manufacturer in late 1997 after the FDA approval of Allegra-D (fexofenadine/pseudoephedrine).
In addition, each compound can have or not have parallel properties, antimuscarinic effects for example.