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A subsequent 1990 study found that the elimination half-life of diphenhydramine was 5.4 hours in children, 9.2 hours in young adults, and 13.5 hours in the elderly. [7] A 1998 study found a half-life of 4.1 ± 0.3 hours in young men, 7.4 ± 3.0 hours in elderly men, 4.4 ± 0.3 hours in young women, and 4.9 ± 0.6 hours in elderly women. [84]
Polonium in the body has a biological half-life of about 30 to 50 days. Caesium in the body has a biological half-life of about one to four months. Mercury (as methylmercury) in the body has a half-life of about 65 days. Lead in the blood has a half life of 28–36 days. [29] [30] Lead in bone has a biological half-life of about ten years.
The shorter elimination half-life of diphenhydramine (4–8 hours) compared to doxylamine may give it an advantage over doxylamine as a sleep aid in this regard. [27] Antihistamines like doxylamine are sedating initially but tolerance occurs with repeated use and can result in rebound insomnia upon discontinuation. [7] [28]
Chlorphenamine produces less sedation than other first-generation antihistamines. [9] A large study on people 65 years old or older linked the development of Alzheimer's disease and other forms of dementia to the "higher cumulative" use of chlorphenamine and other first-generation antihistamines, due to their anticholinergic properties. [10]
H 1 antagonists, also called H 1 blockers, are a class of medications that block the action of histamine at the H 1 receptor, helping to relieve allergic reactions.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.
Loratadine's peak effect occurs after 1–2 hours, and its biological half life is on average eight hours (range 3 to 20 hours) with desloratadine's half-life being 27 hours (range 9 to 92 hours), accounting for its long-lasting effect. [34] About 40% is excreted as conjugated metabolites into the urine, and a similar amount is excreted into ...
Astemizole is a histamine H1-receptor antagonist.It has anticholinergic and antipruritic effects.. Astemizole is rapidly absorbed from the gastrointestinal tract and competitively binds to histamine H 1 receptor sites in the gastrointestinal tract, uterus, blood vessels, and bronchial muscle.
Fexofenadine, sold under the brand name Allegra among others, [10] is an antihistamine pharmaceutical drug used in the treatment of allergy symptoms, such as hay fever and urticaria. [ 11 ] Therapeutically, fexofenadine is a selective peripheral H 1 blocker .