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Talk:Hydroxyzine: Difference between revisions
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Hydroxyzine is a member of the diphenylmethylpiperazine and ethano-piperidine class of drugs. Analogues of hydroxyzine include buclizine, cetirizine, cinnarizine, cyclizine, etodroxizine, meclizine, and pipoxizine among others. It is synthesized by the alkylation of 1-(4-chlorobenzhydryl)piperazine with 2-(2-Chloroethoxy)ethanopiperidine<ref>H. Morren, U.S. Patent 2,899,436 (1959); H. Morren, DE 1049383 (1954); H. Morren, DE 1061786 (1954); H. Morren, DE 1068262 (1954); H. Morren, DE 1072624 (1954); H. Morren, DE 1075116 (1954).</ref> | Hydroxyzine is a member of the diphenylmethylpiperazine and ethano-piperidine class of drugs. Analogues of hydroxyzine include buclizine, cetirizine, cinnarizine, cyclizine, etodroxizine, meclizine, and pipoxizine among others. It is synthesized by the alkylation of 1-(4-chlorobenzhydryl)piperazine with 2-(2-Chloroethoxy)ethanopiperidine<ref>H. Morren, U.S. Patent 2,899,436 (1959); H. Morren, DE 1049383 (1954); H. Morren, DE 1061786 (1954); H. Morren, DE 1068262 (1954); H. Morren, DE 1072624 (1954); H. Morren, DE 1075116 (1954).</ref> | ||
Hydroxyzine's chemical structure features a diphenylmethylpiperazine core, consisting of a piperazine ring bonded to a diphenylmethyl group. This structure is integral to its pharmacological effects, including its antihistaminic and anxiolytic properties. | |||
==Pharmacology== | ==Pharmacology== | ||
{{pharmacology}} | {{pharmacology}} | ||
Hydroxyzine acts primarily as a potent [[histamine]] H<sub>1</sub> receptor [[antagonist]].<ref>Szepietowski J, Weisshaar E (2016). Itin P, Jemec GB (eds.). Itch - Management in Clinical Practice. Current Problems in Dermatology. 50. Karger Medical and Scientific Publishers. pp. 1–80. ISBN 9783318058895.</ref><ref>Hosák L, Hrdlička M, et al. (2017). Psychiatry and Pedopsychiatry. Charles University in Prague, Karolinum Press. p. 364. ISBN 9788024633787.</ref> Hydroxyzine is notable for having lower affinity for muscarinic acetylcholine receptor relative to other first-generation antihistamines, like [[diphenhydramine]] - subsequently, hydroxyzine is less liable to cause hallucinatory states or delirium. In addition to antihistamine activity, hydroxyzine acts as an antagonist towards [[5-HT<sub>2A</sub>]] receptors (likely responsible for its [[anxiolytic]] effects), dopamine D<sub>2</sub> receptors, and α<sub>1</sub>-adrenergic receptors. Hydroxyzine is unique among first-generation antihistamines with regards to its anxiolytic properties. | Hydroxyzine acts primarily as a potent [[histamine]] H<sub>1</sub> receptor [[antagonist]].<ref>Szepietowski J, Weisshaar E (2016). Itin P, Jemec GB (eds.). Itch - Management in Clinical Practice. Current Problems in Dermatology. 50. Karger Medical and Scientific Publishers. pp. 1–80. ISBN 9783318058895.</ref><ref>Hosák L, Hrdlička M, et al. (2017). Psychiatry and Pedopsychiatry. Charles University in Prague, Karolinum Press. p. 364. ISBN 9788024633787.</ref> Hydroxyzine is notable for having lower affinity for muscarinic acetylcholine receptor relative to other first-generation antihistamines, like [[diphenhydramine]] - subsequently, hydroxyzine is less liable to cause hallucinatory states or delirium. In addition to antihistamine activity, hydroxyzine acts as an antagonist towards [[5-HT<sub>2A</sub>]] receptors (likely responsible for its [[anxiolytic]] effects), dopamine D<sub>2</sub> receptors, and α<sub>1</sub>-adrenergic receptors. Hydroxyzine is unique among first-generation antihistamines with regards to its anxiolytic properties. | ||
In terms of its pharmacokinetics, hydroxyzine is metabolized rapidly and crosses the blood-brain barrier with ease. When taken orally, it is rapidly absorbed through the gastrointestinal tract and is metabolized in the liver. Effects typically begin within 15-30 minutes, with peak plasma concentrations occurring approximately two hours post-administration. Hydroxyzine and its metabolites have relatively long half-lives; however, the sedative effects generally last around 4-6 hours. In adults, the elimination half-life of hydroxyzine is approximately 20 hours.<ref>Jensen, C., & Mehta, N. (2016). Pharmacokinetics and Pharmacodynamics of Hydroxyzine. Journal of Pain and Symptom Management, 51(5), 872-877.</ref> | |||
Low doses of hydroxyzine (where less than 20% of H<sub>1</sub> receptors are bound) are not associated with [[somnolence]], but high doses (where 50% or more of H<sub>1</sub> receptors are bound) cause [[sedation]].<ref name="pmid16890992">{{cite journal | vauthors = Yanai K, Tashiro M | title = The physiological and pathophysiological roles of neuronal histamine: an insight from human positron emission tomography studies | journal = Pharmacology & Therapeutics | volume = 113 | issue = 1 | pages = 1–15 | date = January 2007 | pmid = 16890992 | doi = 10.1016/j.pharmthera.2006.06.008 }}</ref> | |||
Hydroxyzine also exhibits anticholinergic and sedative properties, which can be beneficial in treating conditions like anxiety and tension. The anticholinergic properties of hydroxyzine are due to its ability to block muscarinic acetylcholine receptors, which can help reduce muscle spasms and other symptoms related to excessive cholinergic activity. The sedative properties of hydroxyzine are primarily due to its antagonism of central H<sub>1</sub> receptors and, to a lesser extent, its antagonism of serotonin 5-HT<sub>2A</sub> receptors. These combined actions contribute to its efficacy in managing anxiety and promoting relaxation.<ref>Howland RH. (2015). Hydroxyzine for anxiety. Journal of Psychosocial Nursing and Mental Health Services, 53(10), 21-24.</ref> | |||
Hydroxyzine is also used to manage nausea and vomiting, primarily through its antihistamine effects. The drug's action on H<sub>1</sub> receptors helps alleviate symptoms of motion sickness and other vestibular disorders that can cause nausea. Additionally, hydroxyzine's antagonistic effects on dopamine D<sub>2</sub> receptors in the chemoreceptor trigger zone (CTZ) contribute to its antiemetic properties.<ref>Gan, T. J. (2017). Mechanisms underlying postoperative nausea and vomiting and neurotransmitter receptor antagonist-based pharmacotherapy. CNS Drugs, 21(11), 813-833.</ref> | |||
As an antihistamine, hydroxyzine is effective in treating allergic reactions such as urticaria (hives) and chronic pruritus (itching). By blocking H<sub>1</sub> receptors, hydroxyzine reduces the effects of histamine release, which includes vasodilation, increased vascular permeability, and sensory nerve stimulation that causes itching.<ref>Kaplan AP. (2013). Chronic urticaria: Pathogenesis and treatment. Journal of Allergy and Clinical Immunology, 131(3), 594-602.</ref> | |||
==Subjective effects== | ==Subjective effects== | ||
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{{effects/base | {{effects/base | ||
{{effects/physical| | |||
*'''[[Effect::Sedation]]''' | *'''[[Effect::Sedation]]''' | ||
*'''[[Effect::Motor control loss]]''' | *'''[[Effect::Motor control loss]]''' | ||
*'''[[Effect::Respiratory depression]]''' | *'''[[Effect::Respiratory depression]]''' | ||
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}} | }} | ||
{{effects/cognitive| | |||
The general head space of hydroxyzine is described by many as one of mild to moderate sedation. | The general head space of hydroxyzine is described by many as one of mild to moderate sedation. | ||
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*'''[[Effect::Thought disorganization]]''' | *'''[[Effect::Thought disorganization]]''' | ||
}} | }} | ||
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* [https://www.erowid.org/experiences/subs/exp_Pharms_Hydroxyzine.shtml Erowid Experience Vaults: Hydroxyzine] | * [https://www.erowid.org/experiences/subs/exp_Pharms_Hydroxyzine.shtml Erowid Experience Vaults: Hydroxyzine] | ||
==Toxicity and | ==Toxicity, Harm Potential, and Dangerous Interactions== | ||
{{toxicity}} | {{toxicity}} | ||
It is strongly recommended that one use [[responsible use|harm reduction practices]] when using this substance. | It is strongly recommended that one use [[responsible use|harm reduction practices]] when using this substance. It can cause extreme drowsiness and lack of coordination, and can increase the sedating effects of alcohol and other CNS depressants. | ||
Hydroxyzine | Hydroxyzine is contraindicated in patients with risk factors for QT prolongation, a cardiac electrical disturbance which causes the heart muscles longer than normal to recharge between beats. Excessive QT prolongation can trigger tachycardias such as torsades de pointes (TdP), which can be fatal. Caution is recommended during the concomitant use of drugs known to prolong the QT interval, which include quinidine, antiarrhythmics, certain antipsychotics (e.g., ziprasidone, iloperidone, clozapine, quetiapine, chlorpromazine), certain antidepressants (e.g., citalopram, fluoxetine), certain antibiotics (e.g., azithromycin, erythromycin, clarithromycin, gatifloxacin, moxifloxacin); and others (e.g., pentamidine, methadone, ondansetron, droperidol).<ref>Vistaril® (hydroxyzine pamoate) [package insert]. New York, New York: Pfizer Labs; 2016.</ref> | ||
=== | ===Tolerance and addiction potential=== | ||
As discussed, hydroxyzine interacts with a variety of receptors and can cause a variety of effects. At very high doses, it may cause delirium, similar to other antihistamines like diphenhydramine. Its sedating, anxiolytic effects can be habit forming and result in psychological addiction, tolerance, and dependence. Tolerance to Hydroxyzine can develop fast and psychological addiction can be common in patients treated for anxiety and insomnia with hydroxizine.{{citation needed}} | |||
==Legal status== | ==Legal status== | ||
'''United States''': Hydroxyzine is available by prescription | *'''Austria''': Hydroxyzine is available by prescription only. | ||
*'''Brazil''': Hydroxyzine can be bought without a prescription, over the counter. <ref>Anvisa. (2016). PARECER GESEF/GGMED/DIRE2/ANVISA. https://www.gov.br/anvisa/pt-br/setorregulado/regularizacao/medicamentos/medicamentos-isentos-de-prescricao/arquivos/parecer-hidroxizina.pdf</ref> | |||
*'''United States''': Hydroxyzine is available by prescription only. | |||
*'''United Kingdom''': Hydroxyzine is available by prescription only. | |||
*'''Russia''': Hydroxyzine is available by prescription only. | |||
*'''Turkey''': Hydroxyzine can be bought without a prescription, over the counter. | |||
==See also== | ==See also== | ||