Unlike many other first-generation antihistamines, hydroxyzine has very low affinity for the muscarinic acetylcholine receptors, and in accordance, has low or no propensity for producing anticholinergic side effects.
Hydroxyzine can be administered orally or via intramuscular injection.
Because of its antihistamine effects it can be used for the treatment of severe cases of itching, hyperalgesia and motion sickness-induced nausea; it has also been used in some cases to relieve the effects of opioid withdrawal.
Even though it is an effective sedative, hypnotic, and anxiolytic, it shares virtually none of the abuse, dependence, addiction, and toxicity potential of other drugs used for the same range of therapeutic reasons.
Hydroxyzine is prescribed when the onset of an organic disease state manifests through anxiety, as generalized anxiety disorder, or in other more serious cases as psychoneurosis, and is therefore prescribed as a means of regulating normal function.
Unlike hydroxyzine, cetirizine is not reported to appreciably cross the blood-brain barrier, but it has been reported to be associated with dystonic reactions as well as sedation.
If administered in small doses with other substances, such as mentioned, then patients should refrain from using dangerous machinery, motor vehicles or any other practice requiring absolute concentration, in accordance with safety law.
Studies have also been conducted which show that long-term prescription of hydroxyzine can lead to tardive dyskinesia after years of use, but effects related to dyskinesia have also anecdotally been reported after periods of 7.5 months, such as continual head rolling, lip licking and other forms of athetoid movement.
While there are reports of the "hallucinogenic" or "hypnotic" properties of hydroxyzine, several clinical data trials have not reported such side effects from the sole consumption of hydroxyzine, but rather, have described its overall calming effect described through the stimulation of areas within the formatio reticularis.
The hallucinogenic or hypnotic properties have been described as being an additional effect from overall central nervous system suppression by other CNS agents, such as lithium or ethanol.