Although it is a sedative antihistamine, its effects are less intense than many other drugs of this nature.
The side effects of clemastine are greatly dependent on the dose, and sometimes can produce contradictory responses.
Diphenhydramine was the first antihistamine approved by the FDA (in the 1940s) and is widely used in OTC sleeping pills.
Many generic sleep aids consist solely of one active ingredient – diphenhydramine.
However, some feel the trade-off to stop insomnia is worth it.
There is also the possibility of drug resistance where the body adapts to the antihistimine and it doesn’t work as well.
Profound drowsiness is a very common side effect, as is dizziness, difficulty concentrating, and urinary retention.
Hydroxyzine is used for allergies and to suppress nausea.
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.
(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.
Niaprazine was invented in France, and is used mainly in the European Union.