Clinical data | |
---|---|
Pronunciation | /haɪˈdrɒksɪziːn/ |
Trade names | Atarax, [1] Vistaril, [2] others |
Other names | UCB-4492 |
AHFS/Drugs.com | Monograph |
MedlinePlus | a682866 |
License data |
|
Dependence liability | None [3] |
Routes of administration | By mouth, intramuscular |
Drug class | First-generation antihistamine [4] |
ATC code | |
Legal status | |
Legal status | |
Pharmacokinetic data | |
Bioavailability | High |
Protein binding | 93% |
Metabolism | Liver |
Metabolites | Cetirizine, others |
Elimination half-life | Adults: 20.0 hours [5] [6] Elderly: 29.3 hours [7] Children: 7.1 hours [5] |
Excretion | Urine, feces |
Identifiers | |
| |
CAS Number | |
PubChem CID | |
IUPHAR/BPS | |
DrugBank |
|
ChemSpider | |
UNII |
|
KEGG | |
ChEBI |
|
ChEMBL |
|
CompTox Dashboard (EPA) | |
ECHA InfoCard | 100.000.630 |
Chemical and physical data | |
Formula | C21H27ClN2O2 |
Molar mass | 374.91 g·mol−1 |
3D model (JSmol) | |
| |
| |
(verify) |
Hydroxyzine, sold under the brand names Atarax and Vistaril among others, is an antihistamine medication. [8] It is used in the treatment of itchiness, anxiety, insomnia, and nausea (including that due to motion sickness). [8] It is used either by mouth or injection into a muscle. [8]
Hydroxyzine works by blocking the effects of histamine. [9] It is a first-generation antihistamine in the piperazine family of chemicals. [8] [4] Common side effects include sleepiness, headache, and dry mouth. [8] [9] Serious side effects may include QT prolongation. [9] It is unclear if use during pregnancy or breastfeeding is safe. [8]
It was first made by Union Chimique Belge in 1956 and was approved for sale by Pfizer in the United States later that year. [8] [10] In 2022, it was the 46th most commonly prescribed medication in the United States, with more than 13 million prescriptions. [11] [12]
Hydroxyzine is used in the treatment of itchiness, anxiety, and nausea due to motion sickness. [8]
A systematic review concluded that hydroxyzine outperforms placebo in treating generalized anxiety disorder. Insufficient data were available to compare the drug with benzodiazepines and buspirone. [13]
Hydroxyzine can also be used for the treatment of allergic conditions, such as chronic urticaria, atopic or contact dermatoses, and histamine-mediated pruritus.[ medical citation needed ] These have also been confirmed in both recent and past studies to have no adverse effects on the liver, blood, nervous system, or urinary tract. [14] [ better source needed ]
Use of hydroxyzine for premedication as a sedative has no effects on tropane alkaloids, such as atropine, but may, following general anesthesia, potentiate meperidine and barbiturates, and use in pre-anesthetic adjunctive therapy should be modified depending upon the state of the individual. [14]
Doses of hydroxyzine hydrochloride used for sleep range from 25 to 100 mg. [15] [16] [17] As with other antihistamine sleep aids, hydroxyzine is usually only prescribed for short term or "as-needed" use since tolerance to the CNS (central nervous system) effects of hydroxyzine can develop in as little as a few days. [18] [ non-primary source needed ] A major systematic review and network meta-analysis of medications for the treatment of insomnia published in 2022 found little evidence to inform the use of hydroxyzine for insomnia. [19] A 2023 meta-review concludes that hydroxyzine is effective for inducing sleep onset but less effective for maintaining sleep for eight hours. [20]
Hydroxyzine is contraindicated for subcutaneous or intra-articular administration. [21] [22]
The administration of hydroxyzine in large amounts by ingestion or intramuscular administration during the onset of pregnancy can cause fetal abnormalities. When administered to pregnant rats, mice and rabbits, hydroxyzine caused abnormalities such as hypogonadism with doses significantly above that of the human therapeutic range. [23] [ better source needed ]
In humans, a significant dose has not yet been established in studies and, by default, the Food and Drug Administration (FDA) has introduced contraindication guidelines in regard to hydroxyzine. [23] Use by those at risk for or showing previous signs of hypersensitivity is also contraindicated. [23]
Other contraindications include the administration of hydroxyzine alongside depressants and other compounds which affect the central nervous system; [23] if absolutely necessary, it should only be administered concomitantly in small doses. [23] If administered in small doses with other substances, as mentioned, then patients should refrain from using dangerous machinery, motor vehicles or any other practice requiring absolute concentration, in accordance with safety laws. [23]
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, [24] such as continual head rolling, lip licking and other forms of athetoid movement. In certain cases, elderly patients' previous interactions with phenothiazine derivatives or pre-existing neuroleptic treatment may have contributed to dyskinesia at the administration of hydroxyzine due to hypersensitivity caused by prolonged treatment, [24] and therefore some contraindication is given for short-term administration of hydroxyzine to those with previous phenothiazine use. [24]
Several reactions have been noted in manufacturer guidelines—deep sleep, incoordination, sedation, calmness, and dizziness have been reported in children and adults, as well as others such as hypotension, tinnitus, and headaches. [25] Gastrointestinal effects have also been observed, as well as less serious effects such as dryness of the mouth and constipation caused by the mild antimuscarinic properties of hydroxyzine. [25]
Central nervous system effects such as hallucinations or confusion have been observed in rare cases, attributed mostly to overdosage. [26] [25] Such properties have been attributed to hydroxyzine in several cases, particularly in patients treated for neuropsychological disorders, as well as in cases where overdoses have been observed. 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 reticular formation. 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. [27]
Hydroxyzine exhibits anxiolytic and sedative properties in many psychiatric patients. One study showed that patients reported very high levels of subjective sedation when first taking the drug, but that levels of reported sedation decreased markedly over 5–7 days, likely due to CNS receptor desensitization. Other studies have suggested that hydroxyzine acts as an acute hypnotic, reducing sleep onset latency and increasing sleep duration — also showing that some drowsiness did occur. This was observed more in female patients, who also had greater hypnotic response. [28] The use of sedating drugs alongside hydroxyzine can cause oversedation and confusion if administered at high doses—any form of hydroxyzine treatment alongside sedatives should be done under supervision of a doctor. [29] [26]
Because of the potential for more severe side effects, this drug is on the list to avoid in the elderly. [30]
Site | Ki (nM) | Species | Ref |
---|---|---|---|
5-HT2A | 170 (IC50 ) | Rat | [32] |
5-HT2C | ND | ND | ND |
α1 | 460 (IC50) | Rat | [32] |
D1 | >10,000 | Mouse | [33] |
D2 | 378 560 (IC50) | Mouse Rat | [33] [32] |
H1 | 2.0–19 6.4 100 (IC50) | Human Bovine Rat | [34] [35] [36] [37] [32] |
H2 | ND | ND | ND |
H3 | ND | ND | ND |
H4 | >10,000 | Human | [35] |
mACh | 4,600 10,000 10,000 (IC50) 6,310 (pA2) 3,800 | Human Mouse Rat Guinea pig Bovine | [38] [33] [32] [39] [37] |
VDCC | ≥3,400 (IC50) | Rat | [32] |
Values are Ki (nM), unless otherwise noted. The smaller the value, the more strongly the drug binds to the site. |
Hydroxyzine's predominant mechanism of action is as a potent and selective histamine H1 receptor inverse agonist. [40] [41] This action is responsible for its antihistamine and sedative effects. [40] [41] Unlike many other first-generation antihistamines, hydroxyzine has a lower affinity for the muscarinic acetylcholine receptors, and in accordance, has a lower risk of anticholinergic side effects. [37] [41] [42] [43] In addition to its antihistamine activity, hydroxyzine has also been shown to act more weakly as an antagonist of the serotonin 5-HT2A receptor, the dopamine D2 receptor, and the α1-adrenergic receptor. [32] [40] Similarly to the atypical antipsychotics, the comparably weak antiserotonergic effects of hydroxyzine likely underlie its usefulness as an anxiolytic. [44] Other antihistamines without such properties have not been found to be effective in the treatment of anxiety. [45]
Hydroxyzine crosses the blood–brain barrier easily and exerts effects in the central nervous system. [40] A positron emission tomography (PET) study found that brain occupancy of the H1 receptor was 67.6% for a single 30 mg dose of hydroxyzine. [46] In addition, subjective sleepiness correlated well with the brain H1 receptor occupancy. [46] PET studies with antihistamines have found that brain H1 receptor occupancy of more than 50% is associated with a high prevalence of somnolence and cognitive decline, whereas brain H1 receptor occupancy of less than 20% is considered to be non-sedative. [47]
Hydroxyzine also acts as a functional inhibitor of acid sphingomyelinase. [48]
Hydroxyzine can be administered orally or via intramuscular injection. When given orally, hydroxyzine is rapidly absorbed from the gastrointestinal tract. Hydroxyzine is rapidly absorbed and distributed with oral and intramuscular administration, and is metabolized in the liver; the main metabolite (45%), cetirizine, is formed through oxidation of the alcohol moiety to a carboxylic acid by alcohol dehydrogenase, and overall effects are observed within one hour of administration. Higher concentrations are found in the skin than in the plasma. Cetirizine, although less sedating, is non-dialyzable and possesses similar antihistamine properties. The other metabolites identified include a N-dealkylated metabolite, and an O-dealkylated 1/16 metabolite with a plasma half-life of 59 hours. These pathways are mediated principally by CYP3A4 and CYP3A5. [49] [50] The N-dealykylated metabolite, norchlorcyclizine, bears some structural similarities to trazodone, but it has not been established whether it is pharmacologically active. [51] [52] In animals, hydroxyzine and its metabolites are excreted in feces primarily through biliary elimination. [53] [54] In rats, less than 2% of the drug is excreted unchanged. [54]
The time to reach maximum concentration (Tmax) of hydroxyzine is about 2.0 hours in both adults and children and its elimination half-life is around 20.0 hours in adults (mean age 29.3 years) and 7.1 hours in children. [5] [6] Its elimination half-life is shorter in children compared to adults. [5] In another study, the elimination half-life of hydroxyzine in elderly adults was 29.3 hours. [7] One study found that the elimination half-life of hydroxyzine in adults was as short as 3 hours, but this may have just been due to methodological limitations. [55] Although hydroxyzine has a long elimination half-life and acts, in-vivo, as an antihistamine for as long as 24 hours, the predominant CNS effects of hydroxyzine and other antihistamines with long half-lives seem to diminish after 8 hours. [56]
Administration in geriatrics differs from the administration of hydroxyzine in younger patients; according to the FDA, there have not been significant studies made (2004), which include population groups over 65, which provide a distinction between elderly aged patients and other younger groups. Hydroxyzine should be administered carefully in the elderly with consideration given to possible reduced elimination. [26] [ better source needed ]
Hydroxyzine is a member of the diphenylmethylpiperazine class of antihistamines.[ medical citation needed ]
Hydroxyzine is supplied mainly as a dihydrochloride salt (hydroxyzine hydrochloride) but also to a lesser extent as an embonate salt (hydroxyzine pamoate). [57] [58] [59] The molecular weights of hydroxyzine, hydroxyzine dihydrochloride, and hydroxyzine pamoate are 374.9 g/mol, 447.8 g/mol, and 763.3 g/mol, respectively. [4] Due to their differences in molecular weight, 1 mg hydroxyzine dihydrochloride is equivalent to about 1.7 mg hydroxyzine pamoate. [60]
Analogues of hydroxyzine include buclizine, cetirizine, cinnarizine, cyclizine, etodroxizine, meclizine, and pipoxizine among others.
Hydroxyzine preparations require a doctor's prescription. The drug is available in two formulations, the pamoate and the dihydrochloride or hydrochloride salts. Vistaril, Equipose, Masmoran, and Paxistil are preparations of the pamoate salt, while Atarax, Alamon, Aterax, Durrax, Tran-Q, Orgatrax, Quiess, and Tranquizine are of the hydrochloride salt.
Hypnotic, or soporific drugs, commonly known as sleeping pills, are a class of psychoactive drugs whose primary function is to induce sleep and to treat insomnia (sleeplessness).
H1 antagonists, also called H1 blockers, are a class of medications that block the action of histamine at the H1 receptor, helping to relieve allergic reactions. Agents where the main therapeutic effect is mediated by negative modulation of histamine receptors are termed antihistamines; other agents may have antihistaminergic action but are not true antihistamines.
Diphenhydramine (DPH) is an antihistamine and sedative first developed by George Rieveschl and put into commercial use in 1946. it is available as a generic medication, and also sold under the brand name Benadryl, among others. In 2021, it was the 242nd most commonly prescribed medication in the United States, with more than 1 million prescriptions.
Cetirizine is a second-generation antihistamine used to treat allergic rhinitis, dermatitis, and urticaria (hives). It is taken by mouth. Effects generally begin within thirty minutes and last for about a day. The degree of benefit is similar to other antihistamines such as diphenhydramine, which is a first-generation antihistamine.
Fexofenadine, sold under the brand name Allegra among others, is an antihistamine pharmaceutical drug used in the treatment of allergy symptoms, such as hay fever and urticaria.
Promethazine, sold under the brand name Phenergan among others, is a first-generation antihistamine, sedative, and antiemetic used to treat allergies, insomnia, and nausea. It may also help with some symptoms associated with the common cold and may also be used for sedating people who are agitated or anxious, an effect that has led to some recreational use. Promethazine is taken by mouth (oral), as a rectal suppository, or by injection into a muscle (IM).
Doxylamine is an antihistamine medication used to treat insomnia and allergies, and—in combination with pyridoxine (vitamin B6)—to treat morning sickness in pregnant women. It is available over-the-counter and is typically sold under such brand names as Equate or Unisom, among others; and it is used in nighttime cold medicines (e.g., NyQuil) and pain medications containing acetaminophen and/or codeine to help with sleep. The medication is delivered chemically by the salt doxylamine succinate and is taken by mouth. Doxylamine and other first-generation antihistamines are the most widely used sleep medications in the world. Typical side effects of doxylamine (at recommended doses) include dizziness, drowsiness, grogginess, and dry mouth, among others.
Doxepin is a medication belonging to the tricyclic antidepressant (TCA) class of drugs used to treat major depressive disorder, anxiety disorders, chronic hives, and insomnia. For hives it is a less preferred alternative to antihistamines. It has a mild to moderate benefit for sleeping problems. It is used as a cream for itchiness due to atopic dermatitis or lichen simplex chronicus.
Levocetirizine, sold under the brand name Xyzal, among others, is a second-generation antihistamine used for the treatment of allergic rhinitis and long-term hives of unclear cause. It is less sedating than older antihistamines. It is taken by mouth.
Trimipramine, sold under the brand name Surmontil among others, is a tricyclic antidepressant (TCA) which is used to treat depression. It has also been used for its sedative, anxiolytic, and weak antipsychotic effects in the treatment of insomnia, anxiety disorders, and psychosis, respectively. The drug is described as an atypical or "second-generation" TCA because, unlike other TCAs, it seems to be a fairly weak monoamine reuptake inhibitor. Similarly to other TCAs, however, trimipramine does have antihistamine, antiserotonergic, antiadrenergic, antidopaminergic, and anticholinergic activities.
Trazodone, sold under many brand names, is an antidepressant medication, used to treat major depressive disorder, anxiety disorders, and insomnia. It is a phenylpiperazine compound of the serotonin antagonist and reuptake inhibitor (SARI) class. The medication is taken orally.
Quazepam, sold under the brand name Doral among others, is a relatively long-acting benzodiazepine derivative drug developed by the Schering Corporation in the 1970s. Quazepam is used for the treatment of insomnia, including sleep induction and sleep maintenance. Quazepam induces impairment of motor function and has relatively selective hypnotic and anticonvulsant properties with considerably less overdose potential than other benzodiazepines. Quazepam is an effective hypnotic which induces and maintains sleep without disruption of the sleep architecture.
Estazolam, sold under the brand name Prosom among others, is a tranquilizer medication of the triazolobenzodiazepine (TBZD) class, which are benzodiazepines (BZDs) fused with a triazole ring. It possesses anxiolytic, anticonvulsant, hypnotic, sedative and skeletal muscle relaxant properties. Estazolam is an intermediate-acting oral benzodiazepine. It is used for short-term treatment of insomnia.
Chloropyramine is a classical first-generation antihistamine drug approved in Eastern European countries for the treatment of allergic conjunctivitis, allergic rhinitis, bronchial asthma, and other atopic (allergic) conditions. Related indications for clinical use include angioedema, allergic reactions to insect bites, food and drug allergies, and anaphylactic shock.
Azelastine, sold under the brand name Astelin among others, is a H1 receptor-blocking medication primarily used as a nasal spray to treat allergic rhinitis (hay fever) and as eye drops for allergic conjunctivitis. Other uses may include asthma and skin rashes for which it is taken by mouth. Onset of effects is within minutes when used in the eyes and within an hour when used in the nose. Effects last for up to 12 hours.
Ebastine is a H1 antihistamine with low potential for causing drowsiness.
Antihistamines are drugs which treat allergic rhinitis, common cold, influenza, and other allergies. Typically, people take antihistamines as an inexpensive, generic drug that can be bought without a prescription and provides relief from nasal congestion, sneezing, or hives caused by pollen, dust mites, or animal allergy with few side effects. Antihistamines are usually for short-term treatment. Chronic allergies increase the risk of health problems which antihistamines might not treat, including asthma, sinusitis, and lower respiratory tract infection. Consultation of a medical professional is recommended for those who intend to take antihistamines for longer-term use.
Bilastine is an antihistamine medication used to treat hives (urticaria), allergic rhinitis and itchy inflamed eyes (allergic conjunctivitis) caused by an allergy. It is a second-generation antihistamine and takes effect by selectively inhibiting the histamine H1 receptor, preventing these allergic reactions. Bilastine has an effectiveness similar to cetirizine, fexofenadine, and desloratadine.
Daridorexant, sold under the brand name Quviviq, is an orexin antagonist medication which is used for the treatment of insomnia. Daridorexant is taken by mouth.
Somnifacient, also known as sedatives or sleeping pills, is a class of medications that induces sleep. It is mainly used for treatment of insomnia. Examples of somnifacients include benzodiazepines, barbiturates and antihistamines.
This paper says "The extent of renal excretion of Vistaril has not been determined"