Antihistamines in insomnia : mechanism and side-effects
Antihistamines in insomnia : mechanism and side-effects
Helia reyhani,1,*
1. Student research committee, Anzali International Medical Campus, Guilan University of Medical Sciences, Guilan,Iran
Introduction: Insomnia is a complex disorder that affects a significant population of people and it involves many neurotransmitters including orexin, GABA, histamine, acetylcholine, dopamine, and Serotonin.
Research has shown that people who don’t have enough sleep suffer from depression, low quality of life, and physical dysfunction. The first line of therapy is cognitive-behavioral therapy for insomnia (CBT I). pharmacotherapy includes 4 classes of drugs (benzodiazepine receptor agonist, histamine receptor antagonist, orexin receptor agonist, and melatonin receptor agonist ) named by SEDATIVE HYPNOTIC drugs. Between these drugs, antihistamines aren’t FDA FDA-approved and to use them there have to be special circumstances. The antihistamines themselves are 4 types and only the first type, which can go through the blood-brain barrier (BBB) is used as a of the label drug for insomnia.
Methods: An authentic search was performed using PubMed and Scopus from 2000 to 2023. The search has been done with keywords including “insomnia,” “first-generation antihistamines,” “sedative hypnotics,” “histamine,” and “diphenhydramine”. The Subjects used are, “Role of antihistamine in insomnia”. “First generation antihistamines”. “OTC drugs for insomnia”. “treatment of insomnia”.
Results: We reviewed 10 articles and in the end, we found out that first-generation antihistamines( H1 antagonists ) like diphenhydramine are used as OTC drugs for insomnia which means that they don’t have FDA proof. Using these drugs is not recommended especially in elderly people because of their side effects but we can use them in special circumstances. Their side effects are due to their anticholinergic effects on CNS and cause symptoms like nausea, diarrhea, and fatigue.
Conclusion: The majority of OTC drugs to aid sleep contain diphenhydramine, a nonselective histamine H1 -receptor antagonist that has significant affinity at other receptor subtypes leading to nonspecific side effects, including anticholinergic effects (sedation, dry mouth, blurred vision ). Diphenhydramine has lack of clinical evidence supporting efficacy and safety. In the end, according to research although the first generation antihistamines are OTC drugs for insomnia it’s better to not use them unless the FDA-proven drugs wouldn’t work or the insomnia was combined with an allergic disease.