Antihistamines are bad to take at night? I take a daily allergy medication at night before I go to bed. Please elaborate more and/or post some links to this info. Thank you very much 🙂
I remember this bit of info from 2nd year pharmacology. I just did a cursory google search; I should have specified 1st generation antihistamines like diphenhydramine should be avoided:
1)
http://biopsychiatry.com/antihistamines.htm
ABSTRACT
Allergic diseases are responsible for substantially more disability than is generally realized. Allergic rhinitis alone results in 3.5 million lost workdays and 2 million missed school days in the United States each year. Comorbid conditions such as asthma and sinusitis can be disabling as well, resulting each year in more than 10 million missed school days and more than 73 million days of restricted activity, respectively. Antihistamines continue to be the mainstay of treatment for allergic disorders. In the case of the first-generation antihistamines, however, the treatment may well be worse than the disease. Although these agents are effective H(1)-receptor antagonists, they are also highly lipophilic and readily cross the blood-brain barrier, causing considerable sedation. The second-generation agents are more lipophobic and possess different ionic charges than the first-generation antihistamines. As a result, they are far less likely to cross the blood-brain barrier and, for that reason, cause little if any sedation. In a recent comparative trial, subjects who were treated with the first-generation agent diphenhydramine were found to have significant performance deficits on tests of divided attention, working memory, vigilance, and speed. By contrast, subjects who were treated with the second-generation antihistamine loratadine performed as well as subjects who were treated with placebo.
The sedative effects of the first-generation agents persist well into the next day and thus can potentially interfere with daytime performance and safety even when taken the night before. It is therefore recommended that patients whose occupations require vigilance, divided attention, or concentration receive only second-generation antihistamines.
2)
http://www.ncbi.nlm.nih.gov/pubmed/8170531
Diphenhydramine causes drowsiness and performance decrements in some tasks whereas terfenadine generally does not. This study examined central nervous system (CNS) differences in response to the administration of diphenhydramine (50 mg) and terfenadine (60 mg) up to 3 h after drug administration. Two evoked potential measures, the Brainstem Auditory Evoked Potential and the Pattern Reversal Evoked Potential (PREP), assessed CNS function. Other measures of CNS function, cognitive performance and subjective states administered included Critical Flicker Fusion, the Baddeley Grammatical Reasoning Test, Digit Symbol Substitution, the Profile of Mood States, and the Environmental Symptoms Questionnaire. Significant increases in PREP latencies (N75, P100 and N145) occurred after orally ingesting diphenhydramine. No other significant drug effects were observed.
The significant increase in the PREP latencies indicate diphenhydramine's presence in the cerebral cortex results in a slowing of visual information processing. The lack of significant findings for terfenadine is probably a result of its difficulty in penetrating the blood-brain barrier.
