Antihistamines make your sleepy by antagonizing central histimine-1 (H-1) receptors in the brain.The ones you see in over-the-counter sleep aids are usually diphenhydramine and hydroxyzine.It is sometimes used along with Vitamin B6 to stop morning sickness during pregnancy.Doxylamine is one of the most powerful OTC sedatives in the U. Many patients taking doxylamine encounter dry mouth, nausea, and drowsiness.Like all sleep medications, antihistamines artificially modify a person’s sleep patterns.They sometimes leave people groggy the next day, and the subjective quality of sleep is sometimes less than natural sleep.Although it is a sedative antihistamine, its effects are less intense than many other drugs of this nature.
Many generic sleep aids consist solely of one active ingredient – diphenhydramine.
(There are other types of antihistamines that affect H-2, H-3, and H-4 receptors.) People build up tolerance to them over time and when they stop taking them experience rebound insomnia.
Also called histamine antagonists, antihistamines are administered to fight allergic reactions, in which cases sleepiness is considered a possibly undesirable side effect.
And like other hypnotics, the long-term effectiveness of antihistamines has not been demonstrated in a manner that would satisfy scientists.
Which doesn’t mean they don’t work, only the official science is still agnostic on the matter.