First generation antihistaminic drugs used in the treatment of insomnia – superstitions and evidence

Antihistamines are used for the symptomatic treatment of sleep disorders. The rationale for their use is the par ticipation of the histaminergic system in the subcorti cal network modulating consciousness. This network consists of several subcortical structures that act on the cerebral cortex and thalamus, activating these structures and maintaining wakefulness. The histaminergic system, as one of the activating systems of the brain, contributes to the excitation of the thalamus and the cerebellum, while inhibition of its activity is used to induce drowsi ness. There are only a few clinical studies in the medical literature that provide evidence of the hypnotic effects of I generation antihistamines. The article analyses regi stered indications of the first generation antihistamines and studies of their effectiveness in various indications in the field of psychiatry. These drugs were analyzed by searching in PubMed (www.ncbi.nlm.nih.gov/pubmed) and Web of Science (www.webofknowledge.com) clinical studies on people in whom these drugs were studied in primary sleep disorders. The following terms were used: antihistaminergic drugs AND insomnia, diphen hydramine AND insomnia, doxylamine AND insomnia, hydroxyzine AND insomnia, diphenhydramine AND in somnia, promethazine AND insomnia. The same phrases were also entered in the browser www.google.pl. In summary, there are very few studies on the efficacy of 1st generation antihistamines in the treatment of sleep disorders. Of the first-generation antihistamines, doxy lamine and diphenhydramine have only registered in dications for the treatment of accidental insomnia, but there are no studies justifying the use of hydroxyzine in the treatment of insomnia.