Oral Pruritus in acute and chronic urticaria and dermatosis
Adult: Initially, 25 mg at night, may increase up to 25 mg 3-4 times daily, if necessary, according to clinical response. Max: 100 mg daily. Child: 6 months to 6 years Initially, 5-15 mg daily in divided doses. Dose may be adjusted up to Max 2 mg/kg daily based on patient’s weight. >6 years ≤40 kg: Initially, 15-25 mg daily in divided doses, may increase to 50-100 mg daily in divided doses based on patient’s weight; >40 kg: Same as adult dose. Elderly: Max: 50 mg daily.
Moderate to severe: Reduce total daily dose by 50%.
Hepatic Impairment
Reduce total daily dose by 33%. Severe: Contraindicated.
Administration
May be taken with or without food.
Incompatibility
IM: Incompatible with aminophylline, benzylpenicillin salts, chloramphenicol Na succinate, dimenhydrinate, liposomal doxorubicin HCl, thioridazine and some soluble barbiturates.
Contraindications
Acquired or congenital QT interval prolongation, predisposition to QT interval prolongation and torsade de pointes such as significant electrolyte imbalance (e.g. hypokalaemia, hypomagnesaemia), significant bradycardia, history of cardiac arrhythmia, family history of sudden cardiac death; porphyria. Asthmatic patients with previous serious antihistamine-induced adverse bronchopulmonary effect. Severe liver disease. Pregnancy and lactation. Concomitant use of drugs known to prolong QT interval or induce torsade de pointes (e.g. quinidine, amiodarone).
Special Precautions
Patient with increased intraocular pressure, angle-closure glaucoma, emphysema, chronic bronchitis, asthma, COPD, decreased gastrointestinal motility, stenosing peptic ulcer, pyloroduodenal obstruction, primary biliary cirrhosis, bladder outflow obstruction, urinary retention, prostatic hyperplasia, hyperthyroidism, recent MI, uncompensated heart failure, CV disease, hypertension, myasthenia gravis, dementia, epilepsy; increased potential for convulsions. Patients taking drugs that induce bradycardia and hypokalaemia. Renal and hepatic impairment. Children and elderly.
Adverse Reactions
Significant: CNS depression, tachycardia, palpitation, bronchospasm, extrapyramidal effects, tremor, convulsion, severe injection site reactions (e.g. extensive tissue damage, necrosis, gangrene) with IM administration. Rarely, acute generalised exanthematous pustulosis. Blood and lymphatic system disorders: Agranulocytosis, leucopenia, thrombocytopenia, haemolytic anaemia. Ear and labyrinth disorders: Tinnitus, labrynthitis, vertigo. Eye disorders: Blurred vision, accommodation disorder. Gastrointestinal disorders: Dry mouth, constipation, nausea, vomiting, epigastric pain. General disorders and admin site conditions: Fatigue, asthenia, malaise, pyrexia. Immune system disorders: Urticaria, anaphylaxis, angioedema. Investigations: Abnormal LFTs. Metabolism and nutrition disorders: Porphyria, anorexia. Musculoskeletal and connective tissue disorders: Myalgia. Nervous system disorders: Somnolence, headache, dizziness, paresthesia, dyskinesia. Psychiatric disorders: Insomnia, hallucination, sleep disturbances, slurred speech. Renal and urinary disorders: Urinary retention, dysuria. Reproductive system and breast disorders: Priapism, impotence. Respiratory, thoracic and mediastinal disorders: Thickened respiratory secretion, wheezing, nasal stuffiness. Skin and subcutaneous tissue disorders: Rash, pruritus, alopecia, fixed drug eruption. Vascular disorders: Hypotension, flushing. Potentially Fatal: Torsade de pointes, QT interval prolongation, cardiac arrhythmia, respiratory depression; intravascular haemolysis, thrombosis, and digital gangrene following IV or intra-arterial inj.
Patient Counseling Information
This drug may cause dizziness, drowsiness and reduced physical coordination, if affected, do not drive or operate machinery.
Monitoring Parameters
Monitor blood pressure, mental status, and signs of symptom relief.
Overdosage
Symptoms: Excessive sedation, stupor, somnolence, nausea, vomiting, tachycardia, pyrexia, impaired pupillary reflex, tremor, delirium, hallucination. Followed by decreased level of consciousness, respiratory depression, hypotension, convulsion, coma, cardiorespiratory collapse. Management: Symptomatic and supportive treatment. May consider activated charcoal within 1 hour of ingestion. May employ gastric lavage only if life-threatening amount has been ingested within the previous hour and when airway can be protected following acute ingestion. If hypotension occurs, may administer IV fluids, norepinephrine, dopamine or metaraminol, depending on severity and on the cause of hypotension. Dialysis may be indicated if other agents (e.g. barbiturates) have been ingested concomitantly.
Drug Interactions
May potentiate the CNS depressant effects of opiates (e.g. meperidine) and other analgesics; barbiturates, benzodiazepines, hypnotics, anxiolytics, antiemetics, antiepileptics, other antihistamines, skeletal muscle relaxants, sedatives, anaesthetics. Potentiate antimuscarinic effects of TCAs, MAOIs, and other anticholinergics (e.g. atropine). Increased plasma concentrations with cimetidine, potent CYP3A4, CYP3A5 and alcohol dehydrogenase inhibitors. 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: Increases the risk of cardiac arrhythmia with drugs known to prolong QT interval or induce torsade 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 drugs (e.g. toremifene, vandetanib), and methadone.
Food Interaction
Enhanced CNS depressive effect with alcohol.
Lab Interference
May result to false-positive serum TCA screen. May interfere with the results of methacholine test and allergy skin test. May falsely elevate urinary concentrations of 17-hydroxycorticosteroids in Porter-Silber reaction or Glenn-Nelson method.
Action
Description: Hydroxyzine, a piperazine derivative, competitively blocks histamine 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. It is a sedating antihistamine with antimuscarinic and sedative effects, skeletal muscle relaxing, bronchodilator, antiemetic and analgesic properties. 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. Bioavailability: Approx 80% (oral). Time to peak plasma concentration: Approx 2 hours. Distribution: Widely distributed into most tissues including the bile with the highest concentration in the liver, lungs, spleen, kidneys, and adipose tissue. Crosses the blood-brain barrier and placenta. Volume of distribution: Approx 16±3 L/kg. Metabolism: Mainly metabolised in the liver via oxidation by alcohol dehydrogenase, CYP3A4 and CYP3A5 to cetirizine as the major active metabolite. Excretion: Via urine (as cetirizine: 25% oral; 16% IM). Elimination half-life: Approx 20 hours (cetirizine).
Chemical Structure
Hydroxyzine Source: National Center for Biotechnology Information. PubChem Database. Hydroxyzine, CID=3658, https://pubchem.ncbi.nlm.nih.gov/compound/Hydroxyzine (accessed on Jan. 23, 2020)
N05BB01 - hydroxyzine ; Belongs to the class of diphenylmethane derivatives anxiolytics. Used in the management of anxiety, agitation or tension.
References
Anon. Hydroxyzine. AHFS Clinical Drug Information [online]. Bethesda, MD. American Society of Health-System Pharmacists, Inc. https://www.ahfscdi.com. Accessed 01/04/2019.Anon. Hydroxyzine. Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. https://online.lexi.com. Accessed 01/04/2019.Buckingham R (ed). Hydroxyzine. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 01/04/2019.Hydroxyzine Injection, Solution (General Injectables & Vaccines, Inc). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 01/04/2019.Joint Formulary Committee. Hydroxyzine Hydrochloride. British National Formulary [online]. London. BMJ Group and Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 01/04/2019.Vistaril Capsule and Suspension (Pfizer Laboratories Div Pfizer Inc). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 01/04/2019.
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