Drug Action
Hydroxyzine is a sedating antihistamine which exerts its actions by antagonising the effects of histamine.
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Drug reference
Hydroxyzine is a sedating antihistamine which exerts its actions by antagonising the effects of histamine.
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Pruritus ▶BY MOUTH ▶Child 6 months–5 years: 5–15 mg daily in divided doses, dose adjusted according to weight; maximum 2 mg/kg per day ▶Child 6–17 years (body-weight up to 40 kg): Initially 15–25 mg daily in divided doses, dose increased as necessary, adjusted according to weight; maximum 2 mg/kg per day ▶Child 6–17 years (body-weight 40 kg and above): Initially 15–25 mg daily in divided doses, increased if necessary to 50–100 mg daily in divided doses, dose adjusted according to weight ▶Adult: Initially 25 mg daily, dose to be taken at night; increased if necessary to 25 mg 3–4 times a day ▶Elderly: Initially 25 mg daily, dose to be taken at night; increased if necessary to 25 mg twice daily
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Acquired or congenital QT interval prolongation. predisposition to QT interval prolongation CONTRA-INDICATIONS, FURTHER INFORMATION ▶QT interval prolongation Risk factors for QT interval prolongation include significant electrolyte imbalance, bradycardia, cardiovascular disease, and family history of sudden cardiac death.
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Bladder outflow obstruction. breathing problems. cardiovascular disease. children. decreased gastrointestinal motility. dementia. elderly. epilepsy. hypertension. hyperthyroidism. myasthenia gravis. prostatic hypertrophy (in adults). pyloroduodenal obstruction. stenosing peptic ulcer. susceptibility to angle-closure glaucoma. urinary retention CAUTIONS, FURTHER INFORMATION Elderly patients are particularly susceptible to side-effects; manufacturers advise avoid or reduce dose. Children have an increased susceptibility to side-effects, particularly CNS effects.
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Manufacturer advises hydroxyzine should be avoided in patients with previous hypersensitivity to cetirizine or other piperazine derivatives, and aminophylline.
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MHRA/CHM ADVICE: RISK OF QT-INTERVAL PROLONGATION AND TORSADE DE POINTES (APRIL 2015) Following concerns of heart rhythm abnormalities, the safety and efficacy of hydroxyzine has been reviewed by the European Medicines Agency. The review concludes that hydroxyzine is associated with a small risk of QT- interval prolongation and torsade de pointes; these events are most likely to occur in patients who have risk factors for QT prolongation, e.g. concomitant use of drugs that prolong the QT-interval, cardiovascular disease, family history of sudden cardiac death, significant electrolyte imbalance (low plasma-potassium or plasma-magnesium concentrations), or significant bradycardia. To minimise the risk of such adverse effects, the following dose restrictions have been made and new cautions and contra-indications added: . Hydroxyzine is contra-indicated in patients with prolonged QT-interval or who have risk factors for QT- interval prolongation; . Avoid use in the elderly due to increased susceptibility to the side-effects of hydroxyzine; . Consider the risks of QT-interval prolongation and torsade de pointes before prescribing to patients taking drugs that lower heart rate or plasma- potassium concentration; . In children with body-weight up to 40 kg, the maximum daily dose is 2 mg/kg; Respiratory system . In adults, the maximum daily dose is 100 mg; . In the elderly, the maximum daily dose is 50 mg (if use of hydroxyzine cannot be avoided); . The lowest effective dose for the shortest period of time should be prescribed.
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→Appendix 1: antihistamines, sedating
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▶Rare or very rare Severe cutaneous adverse reactions (SCARs). skin reactions ▶Frequency not known Agranulocytosis. alopecia. anticholinergic syndrome. anxiety. appetite decreased. arrhythmias. asthenia. blood disorder. bronchial secretion viscosity increased. chest tightness. chills. coma. concentration impaired. confusion. constipation. depression. diarrhoea. dizziness. drowsiness. dry mouth. dry throat. dyskinesia (on discontinuation). epigastric pain. fever. flushing. gastrointestinal disorders. haemolytic anaemia. hallucination. headache. hepatic function abnormal. hyperhidrosis. hypotension. irritability. labyrinthitis. leucopenia. malaise. menstruation irregular. movement disorders. myalgia. nasal congestion. nausea. palpitations. paraesthesia. QT interval prolongation. respiratory disorders. respiratory tract dryness. seizure (with high doses). sexual dysfunction. sleep disorders. speech slurred. taste bitter. thrombocytopenia. tinnitus. tremor (with high doses). urinary disorders. vertigo. vision disorders. vomiting SIDE-EFFECTS, FURTHER INFORMATION Paradoxical stimulation may occur rarely, especially with high doses or in the elderly. Drowsiness may diminish after a few days of treatment.
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Manufacturers advise avoid—toxicity in animal studies with higher doses. Use in the latter part of the third trimester may cause irritability, paradoxical excitability, and tremor in the neonate.
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Manufacturer advises avoid—expected to be present in milk but effect unknown.
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Manufacturer advises caution in mild to moderate impairment (increased risk of accumulation); avoid in severe impairment. Dose adjustments Manufacturer advises dose reduction of 33% in mild to moderate impairment.
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Dose adjustments Manufacturers advise reduce daily dose by half in moderate to severe renal impairment. l EFFECT ON LABORATORY TESTS May interfere with methacholine test—manufacturer advises stop treatment 96 hours prior to test. May interfere with skin testing for allergy—manufacturer advises stop treatment one week prior to test.
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There can be variation in the licensing of different medicines containing the same drug. Forms available from special-order manufacturers include: oral suspension, oral solution Tablet CAUTIONARY AND ADVISORY LABELS 2 ▶Hydroxyzine hydrochloride (Non-proprietary) Hydroxyzine hydrochloride 10 mg Hydroxyzine 10mg tablets | 84 tablet P £2.10 DT = £1.20 Hydroxyzine hydrochloride 25 mg Hydroxyzine 25mg tablets | 28 tablet P £1.91 DT = £1.71 ▶Atarax (Alliance Pharmaceuticals Ltd) Hydroxyzine hydrochloride 10 mg Atarax 10mg tablets | 84 tablet P £1.20 DT = £1.20 Hydroxyzine hydrochloride 25 mg Atarax 25mg tablets | 28 tablet P £0.62 DT = £1.71
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Driving and skilled tasks Drowsiness may affect performance of skilled tasks (e.g. cycling or driving); sedating effects enhanced by alcohol.
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Initially 25 mg daily, dose to be taken at night;
First-line fragment. Read the complete Indications and Dose section above.
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