[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Pharmacology](https://durgical.com/en/pharmacology/) › [H1 antihistamines](https://durgical.com/en/pharmacology/classes/h1-antihistamines/) › Hydroxyzine

# Hydroxyzine

## H1 antihistamines?

H1 antihistamines

## Pregnancy: contraindicated?

Hydroxyzine is contraindicated in early pregnancy because animal studies showed fetal abnormalities and human data are inadequate.

A sedating antihistamine used for itch, anxiety and sedation before surgery; it can prolong the QT interval.

Updated Nov 1, 2026

## Quick facts

**Group**
[H1 antihistamines](https://durgical.com/en/pharmacology/classes/h1-antihistamines/)

**Target**
Histamine H1 receptor

**Used for**
Anxiety and tension · Sedation before

**Key effects**
Drowsiness and slowed reactions · Dry mouth

**Monitor**
ECG in patients with heart disease · Skin

**ATC**
N05BB01

No doses: the clinician sets them by the current guideline.

On this page

- The basics Mechanism of action
- Indications
- Adverse effects
- Pharmacokinetics
- Memory aid

- Clinical What the labels mean

- Safety Contraindications
- Key interactions
- What is monitored
- Administration and safety
- Pregnancy and breastfeeding
- Nursing care

- Study Test yourself

- Connections Connections

## Mechanism of action

◎**Histamine H1 receptor**Hydroxyzine

ⓘ The figure shows doxepin, a tricyclic first-generation H1 blocker, in the human H1 receptor; hydroxyzine binds the same site.

**Target in 3D:** Histamine H1 receptor. PDB structure 3RZE (RCSB PDB, public domain). [View the structure at RCSB PDB](https://www.rcsb.org/structure/3RZE) · Drag to rotate · pinch to zoom

Hydroxyzine is a piperazine first-generation H1 inverse agonist. It suppresses histamine-driven itch and wheals and, by entering the brain, calms anxiety and causes sedation without being a benzodiazepine. It is converted in the liver to cetirizine. It can block cardiac potassium channels and prolong the QT interval, especially with other QT-prolonging drugs.

- Hydroxyzine blocks H1 receptors in the skin: less itch
- It enters the brain: calm and sedation
- The liver turns it into cetirizine, also active
- Cardiac potassium-channel block can lengthen the QT

## Indications

- Itch from allergic skin conditions such as urticaria and atopic dermatitis [Urticaria and angioedema →](https://durgical.com/en/conditions/urticaria-and-angioedema/)
- Anxiety and tension (short term) [Generalized anxiety disorder →](https://durgical.com/en/conditions/generalized-anxiety-disorder/)
- Sedation before and after general anaesthesia

## Adverse effects

### Common

- Drowsiness and slowed reactions
- Dry mouth, blurred vision and constipation
- Urinary retention, especially with an enlarged prostate
- Dizziness and poor coordination

### Serious (rare, important)

- QT prolongation and torsades de pointes
- Acute generalised exanthematous pustulosis (AGEP)
- Confusion and over-sedation in older adults

## Contraindications

- Prolonged QT interval
- Early pregnancy
- Hypersensitivity to hydroxyzine, cetirizine or levocetirizine

## Key interactions

**Other drugs known to prolong the QT interval**
Additive QT prolongation and risk of torsades de pointes

**Alcohol, benzodiazepines, opioids and other CNS depressants**
Additive sedation and slowed breathing

**Other anticholinergic drugs (tricyclic antidepressants, oxybutynin, antipsychotics)**
Additive dry mouth, urinary retention, constipation and confusion

## What is monitored

- ECG in patients with heart disease, low potassium or magnesium, or other QT drugs
- Sedation and fall risk
- Skin: stop at the first sign of a pustular rash

## Administration and safety

- Oral tablets, capsules or syrup; intramuscular injection exists (deep muscle, never intravenous, subcutaneous or intra-arterial)
- Its salts (hydrochloride, pamoate) are the same drug: not combined

## Pregnancy and breastfeeding

Hydroxyzine is contraindicated in early pregnancy because animal studies showed fetal abnormalities and human data are inadequate.

## Nursing care

- Check the ECG and electrolytes when there are QT risk factors
- Assess sedation and help with walking
- Ask about pregnancy before starting
- Teach not to drive or operate machinery until the effect is known, and to avoid alcohol

## Pharmacokinetics

**Absorption**
Rapidly absorbed by mouth

**Metabolism**
Liver, partly to cetirizine

**Elimination**
Urine and faeces as metabolites

**Onset and duration**
Calming and antipruritic effect within an hour

## Memory aid

HYDROXYzine: Hush the itch, Hush the nerves, but watch the QT.

## Test yourself

Think of the answer, then tap the question to see it.

## Which ECG finding is a contraindication to hydroxyzine?

A prolonged QT interval.

## Which second-generation antihistamine is a metabolite of hydroxyzine?

Cetirizine.

## What are three uses of hydroxyzine?

Allergic itch, short-term anxiety and sedation around surgery.

[Add to my cards (3)](https://durgical.app/estudiar/?add=/en/pharmacology/hydroxyzine/)

[More Pharmacology questions →](https://durgical.com/en/practice/?f=pharmacology)

## What the labels mean

**Pregnancy: contraindicated**
Hydroxyzine is contraindicated in early pregnancy because animal studies showed fetal abnormalities and human data are inadequate.

## Connections

## Related drugs 3

- [Cetirizine](https://durgical.com/en/pharmacology/cetirizine/)
- [Diphenhydramine](https://durgical.com/en/pharmacology/diphenhydramine/)
- [Promethazine](https://durgical.com/en/pharmacology/promethazine/)

## Related conditions 2

- [Urticaria and angioedema](https://durgical.com/en/conditions/urticaria-and-angioedema/)
- [Generalized anxiety disorder](https://durgical.com/en/conditions/generalized-anxiety-disorder/)

[← Back to the class: H1 antihistamines](https://durgical.com/en/pharmacology/classes/h1-antihistamines/)

Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: [DailyMed - HYDROXYZINE HYDROCHLORIDE tablet, film coated](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=d73a8d3c-66ed-40af-9f1d-b710672a34fb) (DailyMed (U.S. National Library of Medicine), 2026); [Hydroxyzine: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a682866.html) (MedlinePlus (U.S. National Library of Medicine), 2026); [ATCDDD - ATC/DDD Index](https://atcddd.fhi.no/atc_ddd_index/?code=N05BB01) (WHO Collaborating Centre for Drug Statistics Methodology, 2026).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/pharmacology/hydroxyzine/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/hydroxyzine/