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Rezine Side Effects

Generic name: hydroxyzine

Medically reviewed by Last updated on Sep 9, 2022.

Note: This document contains side effect information about hydroxyzine. Some dosage forms listed on this page may not apply to the brand name Rezine.

Applies to hydroxyzine: intramuscular solution.

Serious side effects of Rezine

Along with its needed effects, hydroxyzine (the active ingredient contained in Rezine) may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor or nurse immediately if any of the following side effects occur while taking hydroxyzine:

Incidence not known

  • Bleeding, blistering, burning, coldness, discoloration of the skin, feeling of pressure, hives, infection, inflammation, itching, lumps, numbness, pain, rash, redness, scarring, soreness, stinging, swelling, tenderness, tingling, ulceration, or warmth at the injection site
  • blue-green to black skin discoloration
  • pain, redness, or sloughing of skin at the injection site

Other side effects of Rezine

Some side effects of hydroxyzine may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:


  • Shakiness in the legs, arms, hands, or feet
  • trembling or shaking of the hands or feet

Incidence not known

  • Drowsiness
  • dry mouth

For Healthcare Professionals

Applies to hydroxyzine: compounding powder, intramuscular solution, oral capsule, oral suspension, oral syrup, oral tablet.


The most commonly reported side effects included sleepiness, headache, and tiredness.[Ref]

Nervous system

Very common (10% or more): Sleepiness (up to 13.74%)

Common (1% to 10%): Headache

Rare (0.01% to 0.1%): Convulsion, tremor

Frequency not reported: Anticholinergic activity, central nervous system (CNS) depression, drowsiness, incoordination, involuntary motor activity, psychomotor impairment, stimulation

Postmarketing reports: Dizziness, dyskinesia, dystonia, paresthesia, sedation, seizures, syncope[Ref]


Common (1% to 10%): Tiredness

Frequency not reported: Antimuscarinic effects, lassitude

Postmarketing reports: Asthenia, malaise, pyrexia, sudden death[Ref]


Common (1% to 10%): Dry mouth

Postmarketing reports: Constipation, diarrhea, nausea, vomiting[Ref]


Frequency not reported: QT prolongation, Torsade de Pointes

Postmarketing reports: Cardiac arrest, cardiac arrhythmias, edema, hypotension, ventricular arrhythmias, ventricular fibrillation, ventricular tachycardia[Ref]


Frequency not reported: Hypersensitivity reaction

Postmarketing reports: Allergic reaction, anaphylactic shock, angioedema, hypersensitivity[Ref]


Frequency not reported: Respiratory depression

Postmarketing reports: Bronchospasm[Ref]


Postmarketing reports: Acute generalized exanthematous pustulosis (AGEP), bullous condition (pemphigoids, toxic epidermal necrolysis), dermatitis, erythema, erythema multiforme, fixed drug eruptions, increased sweating, maculopapular rash, pruritus, rash, Stevens-Johnson syndrome, urticaria[Ref]


Postmarketing reports: Aggression, agitation, confusion, depression, disorientation, hallucination, insomnia, tics[Ref]


Postmarketing reports: Dysuria, enuresis, urinary retention[Ref]


Postmarketing reports: Accommodation disorder, blurred vision, oculogyric crisis[Ref]


Postmarketing reports: Hepatitis, liver function tests abnormal[Ref]


Postmarketing reports: Thrombocytopenia[Ref]


Postmarketing reports: Weight gain[Ref]

Frequently asked questions

More about Rezine (hydroxyzine)

Patient resources

Other brands

Vistaril, Atarax, Hyzine

Professional resources

Related treatment guides


1. "Product Information. Vistaril (hydroxyzine)." Pfizer U.S. Pharmaceuticals (2001):

2. "Product Information. Atarax (hydroxyzine)." Pfizer U.S. Pharmaceuticals (2001):

3. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.