Chemical formula: C₂₁H₂₇ClN₂O₂ Molecular mass: 374.904 g/mol PubChem compound: 3658
Hydroxyzine interacts in the following cases:
Hydroxyzine is metabolized by alcohol dehydrogenase and CYP3A4/5 and an increase in hydroxyzine blood concentrations may be expected when hydroxyzine is co-administered with drugs known to be potent inhibitors of these enzymes.
Patients should be warned that hydroxyzine may enhance their response to alcohol, barbiturates, benzodiazepines, hypnotics, opioids, anxiolytics, antipsychotics, antidepressents, antiemetics, antiepileptics, other antihistamines, skeletal muscle relaxants, sedatives, anaesthetics and other CNS depressants
Antimuscarinic side effects (both peripheral and central) may be increased if hydroxyzine is given with antimuscarinics such as atropine and some antidepressants (both tricyclics and MAOIs).
Additive anticholinergic effects may occur if hydroxyzine is administered concomitantly with other anticholinergic agents.
Hydroxyzine is an inhibitor of CYP2D6 and may cause drug-drug interactions with CYP2D6 substrates.
Concomitant administration of hydroxyzine with alcohol enhances its action.
Hydroxyzine is metabolized by alcohol dehydrogenase and CYP3A4/5 and an increase in hydroxyzine blood concentrations may be expected when hydroxyzine is co-administered with drugs known to be potent inhibitors of these enzymes.
For patients with moderate or severe renal impairment, it is recommended that the total daily dosage should be reduced by 50%.
The total daily dose should be reduced by 33%.
Use in patients with severe liver disease should be avoided.
It has been suggested that some sedating antihistamines could mask the warning signs of damage caused by ototoxic drugs such as aminoglycoside antibiotics.
Hydroxyzine may antagonise the effects of anticholinesterase drugs.
Hydroxyzine may antagonise the effects of betahistine.
Cimetidine, 600mg twice a day, has been shown to increase the serum concentrations of hydroxyzine and to decrease peak concentrations of the metabolite cetirizine.
Hydroxyzine has been shown to inhibit and reverse the vasopressor effect of adrenaline.
Concomitant administration of hydroxyzine with phenytoin antagonizes the anticonvulsant effect of phenytoin.
Caution in administration of hydroxyzine is required in patients suffering from increased intraocular pressure.
Caution in administration of hydroxyzine is required in patients suffering from seizure disorders including epilepsy.
Caution in administration of hydroxyzine is required in patients suffering from stenosing peptic ulcer.
Caution in administration of hydroxyzine is required in patients suffering from bladder outflow obstruction.
Caution in administration of hydroxyzine is required in patients suffering from decreased GI motility.
Because of its potential antimuscarinic actions, hydroxyzine should be used with caution in patients suffering from urinary retention.
Patients should be warned of impaired dexterity.
Caution in administration of hydroxyzine is required in patients suffering from hyperthyroidism.
Caution in administration of hydroxyzine is required in patients suffering from hypertension.
Patients should be warned of impaired judgement.
Because of its potential antimuscarinic actions, hydroxyzine should be used with caution in patients suffering from angle-closure glaucoma.
Because of its potential antimuscarinic actions, hydroxyzine should be used with caution in patients suffering from prostatic hyperplasia.
Caution in administration of hydroxyzine is required in patients suffering from cardiovascular disease.
Caution in administration of hydroxyzine is required in patients suffering from dementia.
Caution in administration of hydroxyzine is required in patients suffering from breathing problems (e.g. emphysema, chronic bronchitis).
Caution in administration of hydroxyzine is required in patients suffering from myasthenia gravis.
Hydroxyzine should not be used during pregnancy.
Clinical data in humans are inadequate to establish safety in early pregnancy.
The use of sedating antihistamines in the latter part of the third trimester may cause adverse effects in neonates such as irritability, paradoxical excitability, and tremor.
Animal studies have shown reproductive toxicity. Foetal abnormalities have been reported when hydroxyzine was administered, at doses substantially above the human therapeutic dose, to the pregnant mouse, rat and rabbit.
Hydroxyzine crosses the placental barrier which may lead to higher foetal than maternal concentrations.
The following events were observed in a neonate whose mother received high dose (600mg per day) hydroxyzine during pregnancy; hypotonia, movement disorders including extrapyramidal disorders, clonic movements, tachypnea and poor feeding.
It is expected that hydroxyzine may be excreted into breast milk. The effects on the nursing infant are unknown. Hydroxyzine should not be given to nursing mothers.
Patients should be warned that hydroxyzine may impair their ability to perform activities requiring mental alertness or physical co-ordination such as operating machinery or driving a vehicle. Concomitant use of hydroxyzine with alcohol or other CNS depressants should be avoided as this may aggravate these effects.
The most common adverse effect of the sedating antihistamines is CNS depression. Effects vary from slight drowsiness to deep sleep, and include lassitude, dizziness, and incoordination. Paradoxical stimulation may occasionally occur, especially at high doses and in children and the elderly. If sedative effects occur, they may diminish after a few days of treatment. Other common adverse effects include headache, psychomotor impairment and antimuscarinic effects.
Undesirable effects are listed by MedDRA System Organ Classes.
Assessment of undesirable effects is based on the following frequency groupings: Very common: ≥1/10, Common: ≥1/100 to <1/10, Uncommon: ≥1/1,000 to <1/100, Rare: ≥1/10,000 to <1/1,000, Very rare: <1/10,000, Not known: cannot be estimated from the available data.
Not known: Blood disorders, including agranulocytosis, leucopenia, haemolytic anaemia, and thrombocytopenia
Not known: Hypersensitivity reactions, anaphylaxis, angioedema
Not known: Porphyria, anorexia
Not known: Agitation, confusion, disorientation, hallucinations, sleep disturbances, depression, increased anxiety, nightmares
Not known: Dyskinesia4, insomnia, sedation, drowsiness, dizziness, weakness, headache, tremor1 convulsions2, psychomotor impairment, paraesthesias, extrapyramidal effects, seizure, coma, somnolence, disturbance in attention, involuntary motor activity3, ataxia, slurred speech, bitter taste in mouth, faintness
Not known: Accommodation disorder, blurred vision
Not known: Tinnitus, labrynthitis, vertigo
Not known: Ventricular arrhythmias (e.g. Torsade de Pointes), QT interval prolongation, tachycardia, palpitation
Not known: Hypotension, flushing
Not known: Bronchospasm, thickened respiratory tract secretions, wheezing, nasal stuffiness, dryness of throat
Not known: Constipation, dryness of the mouth, nausea, vomiting, increased gastric reflux, diarrhoea, epigastric pain, increased GI peristalsis
Not known: Liver dysfunction
Very rare: Stevens-Johnson syndrome, erythema multiforme
Not known: Dermatitis, fixed drug eruption, pruritis, erythema, papular rash, sweating increased, urticaria, hair loss, eczema, acute generalised exanthematous pustulosis (AGEP), toxic epidermal necrolysis
Not known: Myalgia
Not known: Urinary retention, dysuria
Not known: Priapism, impotence, early menses
Not known: Fatigue, malaise, lassitude, pyrexia, dryness of respiratory mucosae, asthenia, tightness of chest, irritability, chills
Not known: Liver function tests abnormal
Footnotes:
1,2,3 reported usually with doses considerably higher than those recommended. Continuous therapy with over 1g/day has been employed in some patients without these effects having been encountered
4 dyskinesia may follow termination of prolonged antihistamine therapy.
Children and the elderly are more susceptible to side-effects.
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