Hydroxyzine hydrochloride

How it works

It antagonises central and peripheral histamine H1 receptors, producing sedative, anxiolytic and antipruritic effects, with additional antimuscarinic activity.

Prescribing in practice

• Hydroxyzine prolongs the QT interval and is contraindicated where there is known prolongation or significant risk factors, so avoid in cardiac risk, use the lowest effective dose for the shortest time, and avoid other QT-prolonging drugs.
• Its antimuscarinic and sedative effects warrant caution in the elderly, in urinary retention, glaucoma and prostatic enlargement.
• It potentiates alcohol and other central nervous system depressants and can impair driving and skilled tasks.

Monitoring

Monitor for excessive sedation, antimuscarinic effects and, where cardiac risk exists, QT-related concerns, with attention to the elderly.

Counselling the patient

• Expect drowsiness and avoid driving or operating machinery if affected.
• Avoid alcohol while taking this medicine.
• Report palpitations or fainting, and use only for the short term as advised.

Evidence & guidelines

MHRA guidance restricting hydroxyzine to the lowest effective dose and shortest duration reflects its recognised risk of QT prolongation.