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Antihistamine (H1 Receptor Antagonist) · For Cats

Atarax dosage reference for cats (Hydroxyzine)

This page's standard weight-based reference is 1.5 mg per kg (0.68 mg per lb), with Every 8-12 hours recorded as the reference frequency. Use the calculator to see the arithmetic for your cat's weight, then confirm the indication, product, and actual dose with a veterinarian.

Onset
30-60 minutes
Duration
8-12 hours
Class
Antihistamine (H1 Receptor Antagonist)

Weight-based calculator estimate from the references listed on this page. This page has not been independently DVM-reviewed — see our methodology .

This information is for educational purposes only. Always consult your veterinarian before giving medication to your pet. Do not use this calculator for emergencies, overdoses, pregnancy, very young animals, very old animals, pets with liver/kidney disease, or pets taking multiple medications.

Each medication page lists the references recorded for its data. The calculator math and editorial presentation are maintained by PetDosageChart; a page is independently DVM-reviewed only when a named reviewer byline appears. See our methodology and limitations.

Hydroxyzine (often known by brand names such as Atarax and Vistaril) is an antihistamine (H1 receptor antagonist) commonly used in veterinary medicine for Allergic dermatitis and itching, Atopic dermatitis, Urticaria (hives), Mild anxiety, and Mast cell tumor management (adjunctive). Understanding the correct dosage, administration, and potential side effects of Hydroxyzine is critical for your cat’s safety and well-being.

A typical Hydroxyzine dose for cats is around 1.5 mg/kg Every 8-12 hours, within a usual range of 1-2 mg/kg. Available forms include Tablet, Capsule, Oral suspension, and Compounded liquid.

Calculator Warning: Use this only as an educational estimate. Your veterinarian may prescribe a different dose based on your pet’s condition, age, weight, other medications, and medical history.

Hydroxyzine Dosage Calculator for Cats

Enter your cat’s weight below to estimate the Hydroxyzine dose from the 1.5 mg/kg guideline. Your veterinarian may adjust it for your cat’s age, condition, and other medications, so treat the result as an educational starting point, not a prescription.

Dosage Calculator · 01

Enter your cat's weight

Quick Dosage Chart

Typical Hydroxyzine amounts for common cat weights, for quick reference:

Dosage Chart · 02

Atarax weight-based reference chart for cats

Scroll sideways to see full table

Weight Lower Reference Standard Reference Upper Reference Frequency
3 lbs (1.4 kg) 1.4 mg 2.1 mg 2.8 mg Every 8-12 hours
4 lbs (1.8 kg) 1.8 mg 2.7 mg 3.6 mg Every 8-12 hours
5 lbs (2.3 kg) 2.3 mg 3.4 mg 4.6 mg Every 8-12 hours
6 lbs (2.7 kg) 2.7 mg 4.1 mg 5.4 mg Every 8-12 hours
7 lbs (3.2 kg) 3.2 mg 4.8 mg 6.4 mg Every 8-12 hours
8 lbs (3.6 kg) 3.6 mg 5.4 mg 7.2 mg Every 8-12 hours
9 lbs (4.1 kg) 4.1 mg 6.1 mg 8.2 mg (10mg tablet) Every 8-12 hours
10 lbs (4.5 kg) 4.5 mg 6.8 mg 9.0 mg (10mg tablet) Every 8-12 hours
12 lbs (5.4 kg) 5.4 mg 8.1 mg (10mg tablet) 10.8 mg (10mg tablet) Every 8-12 hours
14 lbs (6.3 kg) 6.3 mg 9.4 mg (10mg tablet) 12.6 mg Every 8-12 hours
16 lbs (7.3 kg) 7.3 mg 10.9 mg (10mg tablet) 14.6 mg Every 8-12 hours
18 lbs (8.2 kg) 8.2 mg (10mg tablet) 12.3 mg (10mg tablet) 16.4 mg Every 8-12 hours
20 lbs (9.1 kg) 9.1 mg (10mg tablet) 13.6 mg 18.2 mg (2 × 10mg) Every 8-12 hours
25 lbs (11.3 kg) 11.3 mg (10mg tablet) 17.0 mg 22.6 mg Every 8-12 hours

Parenthetical tablet amounts are arithmetic comparisons only. They do not account for scoring, release type, concentration, product labeling, or whether this medication is appropriate for an individual animal.

By Weight

Atarax reference by cat weight

Choose a common weight to open its optional reference page. Use the main medication calculator for a different exact weight.

Common-weight pages are convenience views of the same educational reference, not separate medical recommendations.

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How to Give Hydroxyzine to Your Cat

Hydroxyzine tablets or capsules can be given whole, hidden in a pill pocket or small piece of cheese or deli meat. For cats that refuse pills, the tablet can be crushed and mixed into a small amount of strong-flavored wet food, though this may reduce palatability. A compounded flavored liquid is often the easiest option for finicky cats. Use a pill gun to place the pill at the back of the tongue if giving directly, then offer a treat or syringe a small amount of water to ensure it is swallowed. Give with food to minimize stomach upset.

It is generally recommended to give Hydroxyzine with food to help reduce stomach upset. It may interact with CNS depressants (additive sedation), Anticholinergic drugs (additive effects), Epinephrine (hydroxyzine may reverse its vasopressor effect), and Opioids (enhanced sedation and respiratory depression).

Side Effects and Safety

Common side effects include Sedation and drowsiness, Dry mouth, Decreased appetite, and Paradoxical excitement or hyperactivity in some cats. More serious side effects can occur, such as Severe paradoxical agitation, Urinary retention, Cardiac arrhythmias (rare, at high doses), and Seizures (very rare).

Cautions · 12

When Atarax should be used with caution or avoided

Some cats should not take Atarax, or need a different dose and closer monitoring. Tell your veterinarian about your pet's full health history and every other medication or supplement they take before giving Atarax.

  • Known hypersensitivity to hydroxyzine or cetirizine
  • Severe cardiac disease
  • Glaucoma
  • Urinary obstruction

Interactions · 13

Atarax drug interactions

Atarax can interact with other drugs. This list is not complete — always give your veterinarian a full list of your cat's medications and supplements.

CNS depressants (additive sedation)
Anticholinergic drugs (additive effects)
Epinephrine (hydroxyzine may reverse its vasopressor effect)
Opioids (enhanced sedation and respiratory depression)

Calculator Limits · 14

When not to use this calculator

This calculator gives a general educational estimate for a healthy adult cat at a known weight. Do not rely on it in these situations — talk to your veterinarian instead:

  • In an emergency, or after accidental ingestion or a suspected overdose
  • For pregnant or nursing pets
  • For very young or very old cats
  • For pets with liver disease, kidney disease, or another chronic illness
  • For pets taking several medications at once
  • When you are not sure of your cat's current, accurate weight
  • For combination products that contain additional active ingredients

Overdose · 15

Suspected overdose: what to do

If you think your cat had too much Atarax, or swallowed any medication by accident, act right away. Do not wait for symptoms to appear.

  • Call your veterinarian or the nearest emergency animal hospital.
  • ASPCA Animal Poison Control Center: (888) 426-4435
  • Pet Poison Helpline: (855) 764-7661

A consultation fee may apply to the poison hotlines. Have the medication packaging ready, and note how much your pet may have taken and when. Do not try to make your pet vomit unless a veterinarian tells you to.

When to Call the Vet

If your cat experiences any of the following, contact your veterinarian or an emergency clinic immediately:

Frequently Asked Questions

Frequently Asked · 07

Questions about this medication

Can hydroxyzine make my cat hyper instead of sleepy?
Yes, some cats experience a paradoxical reaction to hydroxyzine where they become more agitated and hyperactive instead of sedated. This is more common in cats than in dogs. If your cat becomes unusually restless, vocal, or aggressive after taking hydroxyzine, discontinue the medication and contact your vet. An alternative antihistamine may be better suited for your cat.
Is hydroxyzine better than Benadryl for cats?
Hydroxyzine is often considered more effective than diphenhydramine (Benadryl) for allergic conditions in cats because it has both antihistamine and mild anti-anxiety properties. It also has some mast cell-stabilizing activity. However, response varies between individual cats—some do better on one antihistamine versus another. Your vet can help determine which is the best choice for your cat.
How long does it take for hydroxyzine to help my cat's itching?
Hydroxyzine typically starts working within 30-60 minutes of oral administration. However, for chronic allergic conditions, it may take several days of consistent dosing to see the full benefit. Antihistamines work best as preventatives, so giving them before expected allergen exposure is ideal. If you see no improvement after 2 weeks of regular dosing, consult your vet about alternatives.
Can I give my cat hydroxyzine every day?
Yes, hydroxyzine can be given daily for chronic allergy management in cats. It is generally safe for long-term use when dosed appropriately. Your vet may recommend giving it every 8-12 hours depending on symptom severity. Periodic check-ups are advisable during long-term use to monitor for any side effects.
What is the correct hydroxyzine dose for a cat?
The typical hydroxyzine dose for cats is 1-2 mg/kg given every 8-12 hours. For an average 4 kg cat, this is approximately 5-10 mg per dose. Always start at the lower end to assess your cat's response, as some cats are more sensitive than others. Your veterinarian will determine the ideal dose based on your cat's specific condition and weight.

Use This Guide Safely · 08

What weight alone cannot tell you

The calculator performs one narrow job: it multiplies your cat's weight by the lower, standard, and upper mg/kg values recorded for Atarax. It cannot decide whether this drug, indication, formulation, or schedule is appropriate for an individual animal.

Context in this medication record

Commonly listed uses
Allergic dermatitis and itching, Atopic dermatitis, Urticaria (hives), Mild anxiety, Mast cell tumor management (adjunctive)
Recorded forms
Tablet, Capsule, Oral suspension, Compounded liquid
Reference timing
Every 8-12 hours; onset 30-60 minutes; duration 8-12 hours

Individual checks a calculator cannot perform

  • Confirm the diagnosis and the reason this medication is being considered.
  • Match the exact product, concentration, route, and whether a tablet may be split.
  • Account for age, pregnancy, organ function, genetics, allergies, and prior reactions.
  • Review every prescription, over-the-counter product, and supplement your pet takes.

Recorded cautions

Known hypersensitivity to hydroxyzine or cetirizine; Severe cardiac disease; Glaucoma; Urinary obstruction.

Recorded interactions

CNS depressants (additive sedation); Anticholinergic drugs (additive effects); Epinephrine (hydroxyzine may reverse its vasopressor effect); Opioids (enhanced sedation and respiratory depression).

These lists reproduce the structured record used by this page and may not be exhaustive. Show your veterinarian the product label and your cat's complete medication list before acting on a number.

For Dogs

Looking for Atarax dosage for dogs?

View the Atarax dosage chart and calculator for dogs.

Related · 08

Related medications for cats

Sources · 09

Sources & references

The structured medication record behind this page names the references below. The links open the publisher or official resource; they do not turn this page into a prescription for an individual animal.

Source names are shown at the record level; passage-level page and label citations are still being added. Read our methodology and limitations.

Transparency · 11

How this page was made

This page's structured medication record includes Plumb's Veterinary Drug Handbook among its source names. PetDosageChart applies the record's mg/kg values to the entered weight and presents the arithmetic result. A source record is not the same as an individualized prescription or an independent clinical review.

Sources cited
  • Plumb's Veterinary Drug Handbook
  • Merck Veterinary Manual
Calculator formula
Doses scale linearly from a standard basis of 1.5 mg per kg (0.68 mg per lb) of body weight, given Every 8-12 hours. The calculator multiplies that basis by your cat's weight and shows an arithmetic comparison with recorded tablet sizes. That comparison does not determine whether a tablet is scored, splittable, or appropriate for your pet.
Editorial owner
Prepared and maintained by the PetDosageChart editorial team, a software-led publisher and not a veterinary practice.
DVM review status
Not independently DVM-reviewed. A named reviewer and review date appear here only after a confirmed review.

More on our methodology and editorial process — how we source, calculate, and review cats dosage data.

Safety · 10

More resources