For people who need to get to sleep, however, the drowsiness is the main benefit of antihistamines.These are usually not prescription drugs and can be purchased at retailers over-the-counter.
At higher doses it may result in slurred speech, staggering gait, poor judgment, and slow, uncertain reflexes.
Doses of sedatives such as benzodiazepines, when used as a hypnotic to induce sleep, tend to be higher than amounts used to relieve anxiety, whereas only low doses are needed to provide a peaceful effect.
Sedatives can be misused to produce an overly-calming effect (alcohol being the classic and most common sedating drug).
In the event of an overdose or if combined with another sedative, many of these drugs can cause unconsciousness (see hypnotic) and even death.
(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.