Adult: Initially, 50-100 mg, may be repeated every 4-6 hours as necessary. Switch to oral therapy as soon as possible. Treatment guidelines and dosage recommendations may vary among individual products or between countries (refer to specific product recommendations).
Oral Pruritus
Adult: For the management of cases associated with allergic conditions (e.g. chronic urticaria, atopic and contact dermatitis), and in histamine-mediated pruritus: Initially, 25 mg at night, may be increased to 25 mg 3 or 4 times daily if necessary. Max: 100 mg daily. Dosage must be adjusted according to individual response. Use the lowest effective dose for the shortest possible duration. Treatment guidelines and dosage recommendations may vary among individual products or between countries (refer to specific product recommendations). Elderly: Dosage reduction may be necessary. Max: 50 mg daily. Child: 6 months to 6 years Initially, 5-15 mg daily in divided doses, may be adjusted up to Max of 2 mg/kg daily based on the patient's weight; >6 years weighing ≤40 kg: Initially, 15-25 mg daily in divided doses, may be increased up Max of 2 mg/kg daily to 50-100 mg daily; >40 kg: Same as adult dose. Dosage must be adjusted according to individual response. Use the lowest effective dose for the shortest possible duration. Treatment guidelines and dosage recommendations may vary among individual products or between countries (refer to specific product recommendations).
Oral Adjunct to pre- or post-operative sedation
Adult: 50-100 mg. Dosage must be adjusted according to individual response. Treatment guidelines and dosage recommendations may vary among individual products or between countries (refer to specific product recommendations). Elderly: Initiate at low doses and closely observe the patient. Child: 0.6 mg/kg. Max: 100 mg/dose. Dosage must be adjusted according to individual response. Treatment guidelines and dosage recommendations may vary among individual products or between countries (refer to specific product recommendations).
Oral Short-term management of anxiety
Adult: 50-100 mg daily given in divided doses. Max: 100 mg daily. Dosage must be adjusted according to individual response. Use the lowest effective dose for the shortest possible duration. Treatment guidelines and dosage recommendations may vary among individual products or between countries (refer to specific product recommendations). Elderly: Dosage reduction may be necessary. Max: 50 mg daily.
Renal Impairment
Short-term management of anxiety; Pruritus:
Moderate to severe: Reduce the total daily dose by 50%.
Hepatic Impairment
Short-term management of anxiety; Pruritus:
Mild to moderate: Reduce the total daily dose by 33%. Severe: Contraindicated.
Administration
May be taken with or without food.
Incompatibility
Hydroxyzine hydrochloride IM inj: Incompatible with aminophylline, benzylpenicillin salts, chloramphenicol Na succinate, dimenhydrinate, doxorubicin hydrochloride (in liposomal formulation), thioridazine, and some soluble barbiturates.
Contraindications
Known acquired or congenital QT interval prolongation; risk factors for QT interval prolongation, including significant electrolyte imbalance (e.g. hypokalaemia, hypomagnesaemia), known CV disease, significant bradycardia, and family history of sudden cardiac death; porphyria. Asthmatic patients with previous experience of serious antihistamine-induced adverse bronchopulmonary effect. Severe hepatic impairment. Pregnancy and lactation. Concomitant use of drugs known to prolong QT interval or induce torsades de pointes.
Special Precautions
Patient with angle-closure glaucoma, asthma, COPD, prostatic hyperplasia and/or urinary stricture, bladder outflow obstruction, decreased gastrointestinal motility, epilepsy, myasthenia gravis, hypertension, hyperthyroidism. Inj: Not for SC, intra-arterial or IV administration. Renal and mild to moderate hepatic impairment. Children and elderly.
Adverse Reactions
Significant: CNS depression (e.g. dizziness, drowsiness), severe inj site reactions (e.g. extensive tissue damage, necrosis, gangrene) following IM administration; intravascular haemolysis, thrombosis, and digital gangrene (if given via IV or intra-arterial inj); significant tissue damage (if given via SC inj). Rarely, acute generalised exanthematous pustulosis. Blood and lymphatic system disorders: Agranulocytosis, leucopenia, thrombocytopenia, haemolytic anaemia. Cardiac disorders: Tachycardia, palpitation. Ear and labyrinth disorders: Tinnitus, vertigo. Eye disorders: Blurred vision, accommodation disorder. Gastrointestinal disorders: Xerostomia, constipation, nausea, vomiting, epigastric pain, diarrhoea, increased gastrointestinal peristalsis. General disorders and administration site conditions: Fatigue, pyrexia, malaise, chills, ataxia, irritability. Immune system disorders: Hypersensitivity reactions (e.g. anaphylaxis, angioedema). Investigations: Abnormal LFTs, increased weight. Metabolism and nutrition disorders: Anorexia, porphyria. Nervous system disorders: Headache, paraesthesia, extrapyramidal effects, seizures, Psychiatric disorders: Insomnia, agitation, confusion, sleep disturbances, depression, hallucination Renal and urinary disorders: Urinary retention, dysuria. Reproductive system and breast disorders: Early menses, priapism, impotence. Respiratory, thoracic and mediastinal disorders: Nasal stuffiness, dry throat, wheezing. Skin and subcutaneous tissue disorders: Dermatitis, papular rash, erythema, eczema, hair loss, toxic epidermal necrolysis, Stevens-Johnson syndrome. Vascular disorders: Hypotension, flushing.
Patient Counseling Information
This drug may cause dizziness and drowsiness, if affected, do not drive or operate machinery.
Monitoring Parameters
Monitor blood pressure, mental status and alertness, and relief of symptoms. Assess for signs and symptoms of hypersensitivity reactions and rash, including worsening of pre-existing skin reactions.
Overdosage
Symptoms: Excessive sedation, flushing, nausea, vomiting, dilated pupils, dry mouth and tongue, hot dry skin, fever, sinus tachycardia, ataxia, nystagmus, agitation, stupor, delirium, visual hallucinations, postictal depression, coma, and convulsions which may progress to respiratory failure and CV collapse. Management: Symptomatic and supportive treatment. May consider activated charcoal within 1 hour of ingestion. May perform gastric lavage only if life-threatening amount has been ingested within the previous hour and if the airway can be protected adequately. Maintain clear airways and provide adequate ventilation. Monitor blood pressure, pulse, and temperature. Perform a 12-lead ECG and monitor heart rhythm. May administer IV fluids for hypotension, and if severe hypotension persists, may give norepinephrine, dopamine, or dobutamine depending on the cause of hypotension. Dialysis may be indicated if other agents (e.g. barbiturates) have been ingested concomitantly.
Drug Interactions
May enhance the CNS depressant effects of other antihistamines, barbiturates, benzodiazepines, hypnotics, anxiolytics, antiemetics, antiepileptics, skeletal muscle relaxants, sedatives, opioids, and anaesthetics. Central and peripheral antimuscarinic side effects may be increased with TCAs, MAOIs, and antimuscarinic agents (e.g. atropine). Inhibits and reverses the vasopressor effect of epinephrine. May antagonise the effects of betahistine and anticholinesterase drugs. May mask the signs of damage caused by ototoxic agents (e.g. aminoglycosides). Potentially Fatal: Increased risk of cardiac arrhythmia with drugs known to prolong QT interval or induce torsades de pointes such as class IA (e.g. quinidine, disopyramide) and class III antiarrhythmics (e.g. amiodarone, sotalol), some antipsychotics (e.g. haloperidol), some antidepressants (e.g. escitalopram, citalopram), some antimalarials (e.g. mefloquine), some antibiotics (e.g. erythromycin, levofloxacin), some gastrointestinal agents (e.g. prucalopride), some anti-cancer agents (e.g. toremifene, vandetanib), and methadone.
Food Interaction
Enhanced CNS depressive effect with alcohol.
Lab Interference
May lead to false-positive serum TCA screen. May interfere with the results of methacholine test and allergy skin test. May cause falsely-elevated urinary concentrations of 17-hydroxycorticosteroids using the Porter-Silber reaction or Glenn-Nelson method.
Action
Description: Mechanism of Action: Hydroxyzine is a 1st generation piperazine derivative antihistamine with sedative effects, and CNS depressant, anticholinergic, antispasmodic, local anaesthetic, antiemetic, and primary skeletal muscle relaxant properties. It competitively blocks histamine at H1-receptors on effector cells of the gastrointestinal tract, blood vessels, and respiratory tract, thereby inhibiting H1-receptor-mediated reactions such as vasodilation, flare and itch reactions, and sneezing. Onset: Sedative action: 15-30 minutes (oral); rapid (IM). Duration: Sedative action: 4-6 hours (oral). Decreased histamine-induced wheal and flare areas: 2 to ≥36 hours. Suppression of pruritus: 1-12 hours. Pharmacokinetics: Absorption: Rapidly absorbed from the gastrointestinal tract. Time to peak plasma concentration: Approx 2 hours (oral). Distribution: Widely distributed into most tissues, including the bile. Crosses the blood-brain barrier and placenta. Volume of distribution: Approx 16 ± 3 L/kg. Metabolism: Metabolised in the liver by alcohol dehydrogenase, CYP3A4 and CYP3A5 isoenzymes to form several metabolites including cetirizine (active metabolite). Excretion: Via urine. Elimination half-life: Approx 20 hours (cetirizine).
Chemical Structure
Hydroxyzine Source: National Center for Biotechnology Information. PubChem Compound Summary for CID 3658, Hydroxyzine. https://pubchem.ncbi.nlm.nih.gov/compound/Hydroxyzine. Accessed Mar. 30, 2023.
Storage
Tab, oral susp: Store between 20-25°C. Cap, solution for IM inj: Store between 15-30°C. Protect from light.
N05BB01 - hydroxyzine ; Belongs to the class of diphenylmethane derivatives anxiolytics. Used in the management of anxiety, agitation or tension.
References
AA Pharma Hydroxyzine Capsule (Pharmaforte Singapore Pte. Ltd.). MIMS Singapore. http://www.mims.com/singapore. Accessed 10/10/2022.Anon. Hydroxyzine. AHFS Clinical Drug Information [online]. Bethesda, MD. American Society of Health-System Pharmacists, Inc. https://www.ahfscdi.com. Accessed 10/10/2022.Anon. Hydroxyzine. Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. https://online.lexi.com. Accessed 10/10/2022.Atarax 25 mg Film-coated Tablets (DHP Healthcare Limited). MHRA. https://products.mhra.gov.uk. Accessed 10/10/2022.Buckingham R (ed). Hydroxyzine. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 10/10/2022.Hydroxyzine Hydrochloride Injection, Solution (Henry Schein, Inc.). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed. Accessed 10/10/2022.Hydroxyzine Hydrochloride Tablet (Northstar Rx LLC). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed. Accessed 10/10/2022.Joint Formulary Committee. Hydroxyzine. British National Formulary [online]. London. BMJ Group and Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 10/10/2022.Vistaril Capsule and Suspension (Pfizer Laboratories Div Pfizer Inc). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed. Accessed 10/10/2022.
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