Hydroxyzine is an antihistamine with a calming effect, used for tension anxiety, intense itching (allergies, urticaria) and light sedation before procedures. Unlike traditional anxiolytics, it does not cause dependence.
Also known as: Atarax, Vistaril
Hydroxyzine plus midazolam causes additive sedation with respiratory depression risk.
Hydroxyzine (sedating antihistamine) depresses the CNS; midazolam is a short-acting benzodiazepine.
Level of consciousness and respiratory rate after dosing.
Persistent drowsiness, slow breathing.
Avoid outside a controlled setting; reduce doses and monitor breathing.
EMC-UK — Hydroxyzine SmPC, CNS depression with depressants: https://www.medicines.org.uk/emc/product/8740
Hydroxyzine plus morphine increases the risk of profound sedation, hypotension and respiratory depression.
Opioid plus sedating antihistamine: additive depression of the CNS and respiratory centre.
Level of consciousness, respiratory rate, blood pressure.
Extreme drowsiness, slow breathing, hypotension.
If the combination is needed (analgesic premedication), reduce doses and monitor respiration.
DailyMed — Morphine Sulfate Injection [Fresenius Kabi] label (additive CNS depressants) and Hydroxyzine Pamoate [RemedyRepack]: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=1f53de80-efc8-4930-b3e3-fba0d026af05
Atropine plus hydroxyzine adds anticholinergic effects (tachycardia, dry mouth, urinary retention) and sedation.
Both have anticholinergic activity; hydroxyzine adds H1-blockade sedation.
Heart rate, urination, level of consciousness.
Tachycardia, urinary retention, paradoxical agitation.
In premedication, doses should be reduced; monitor for anticholinergic signs.
DailyMed — Atropine Sulfate Injection and Hydroxyzine Pamoate labels (additive anticholinergic effects): https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=8663ff94-8bea-4061-9fd5-3ab2e85e862e
Alcohol adds CNS sedation and depression to hydroxyzine (Prontuário 10.1 — additive sedative effects).
Avoid alcohol during treatment.
EMC-UK — Hydroxyzine SmPC 4.4/4.5 (alcohol); Prontuário 10.1.
Hydroxyzine prolongs QT — contraindicated with pre-existing long QT or other prolongers.
ECG if risk factors; review concomitants.
EMC-UK — hydroxyzine SmPC 4.3/4.4 (QT).
Avoid in the 1st trimester and near term (antimuscarinic effects on the newborn).
Use only if clearly necessary.
EMC-UK — hydroxyzine SmPC 4.6 (pregnancy).
Annex 1 records "See Antihistamines H1. Should be avoided" (factor C): hydroxyzine should be avoided in pregnancy, especially in the 1st trimester and near term. If an antihistamine is indispensable, prefer alternatives with more data (loratadine, cetirizine) or chlorphenamine.
Avoid; use only if there is no alternative and benefit justifies, at the lowest dose and duration possible.
Hydroxyzine refers to "Antihistamines H1" in Annex 2: "significant amounts of some antihistamines in milk... avoidance recommended: drowsiness with clemastine" — avoid breastfeeding during treatment.
Prontuário Terapêutico INFARMED — Annex 1: "Hydroxyzine — See Antihistamines H1. Should be avoided" (l. 40499); Annex 2: Antihistamines H1 (l. 42199). EMC-UK (MHRA) — Hydroxyzine SmPC (Atarax).
Clinical and educational support tool. The information does not replace a medical prescription or the opinion of a qualified healthcare professional.
Sedating first-generation antihistamine with dual clinical use: antipruritic/antiallergic and non-dependence-forming anxiolytic; partially active metabolite (cetirizine) with less sedation.
Central and peripheral H1 antagonist (sedation, anxiolysis, antipruritus) with moderate muscarinic antagonism (mild anticholinergic effects) and alpha-1 (discrete hypotension). Documented QT prolongation (hERG blockade) — dose-dependent and a current regulatory concern (short high-dose courses).
Oral: rapid good absorption (> 80%), peak 2 h, clinical onset 15–60 min. IM: rapid (peak ~1 h). Food does not significantly change extent.
Almost complete hepatic metabolism (mainly CYP2D6 and CYP3A4) to cetirizine (active metabolite, potent peripheral H1 with less BBB passage); renal excretion of cetirizine and metabolites. Renal/hepatic impairment: lengthen interval.
~20 h (adults); 7–12 h in children (more frequent weight-based doses). Cetirizine (metabolite): 8–9 h.
Medicines from the same therapeutic group (ATC classification) or the same pharmacological class.
