Non-steroidal anti-inflammatory drug (NSAID) · For Cats

Onsior dosage reference for cats (Robenacoxib)

This page's standard weight-based reference is 1 mg per kg (0.45 mg per lb), with once daily (max 3 consecutive days for cats) 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: 24 hours
Class: Non-steroidal anti-inflammatory drug (NSAID)

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.

Robenacoxib (often known by brand names such as Onsior) is a non-steroidal anti-inflammatory drug (NSAID) commonly used in veterinary medicine for post-surgical pain, acute pain, inflammation, and soft tissue surgery pain. Understanding the correct dosage, administration, and potential side effects of Robenacoxib is critical for your cat’s safety and well-being.

A typical Robenacoxib dose for cats is around 1 mg/kg once daily (max 3 consecutive days for cats), within a usual range of 1-2.4 mg/kg. Available forms include tablet and injectable.

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.

Robenacoxib Dosage Calculator for Cats

Enter your cat’s weight below to estimate the Robenacoxib dose from the 1 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 Robenacoxib amounts for common cat weights, for quick reference:

Dosage Chart · 02

Onsior 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	1.4 mg	3.4 mg	once daily (max 3 consecutive days for cats)
4 lbs (1.8 kg)	1.8 mg	1.8 mg	4.3 mg	once daily (max 3 consecutive days for cats)
5 lbs (2.3 kg)	2.3 mg	2.3 mg	5.5 mg (6mg tablet)	once daily (max 3 consecutive days for cats)
6 lbs (2.7 kg)	2.7 mg	2.7 mg	6.5 mg (6mg tablet)	once daily (max 3 consecutive days for cats)
7 lbs (3.2 kg)	3.2 mg	3.2 mg	7.7 mg	once daily (max 3 consecutive days for cats)
8 lbs (3.6 kg)	3.6 mg	3.6 mg	8.6 mg	once daily (max 3 consecutive days for cats)
9 lbs (4.1 kg)	4.1 mg	4.1 mg	9.8 mg	once daily (max 3 consecutive days for cats)
10 lbs (4.5 kg)	4.5 mg (6mg tablet)	4.5 mg (6mg tablet)	10.8 mg (2 × 6mg)	once daily (max 3 consecutive days for cats)
12 lbs (5.4 kg)	5.4 mg (6mg tablet)	5.4 mg (6mg tablet)	13.0 mg (2 × 6mg)	once daily (max 3 consecutive days for cats)
14 lbs (6.3 kg)	6.3 mg (6mg tablet)	6.3 mg (6mg tablet)	15.1 mg	once daily (max 3 consecutive days for cats)
16 lbs (7.3 kg)	7.3 mg (6mg tablet)	7.3 mg (6mg tablet)	17.5 mg (3 × 6mg)	once daily (max 3 consecutive days for cats)
18 lbs (8.2 kg)	8.2 mg	8.2 mg	19.7 mg	once daily (max 3 consecutive days for cats)
20 lbs (9.1 kg)	9.1 mg	9.1 mg	21.8 mg	once daily (max 3 consecutive days for cats)
25 lbs (11.3 kg)	11.3 mg (2 × 6mg)	11.3 mg (2 × 6mg)	27.1 mg	once daily (max 3 consecutive days for cats)

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

Onsior 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 Robenacoxib to Your Cat

IMPORTANT: Onsior for cats is FDA-approved for a MAXIMUM of 3 consecutive days only. This is different from dogs, where longer courses may be used. Give without food for best absorption, at least 30 minutes before or after a meal. The tablet is small and flavored. Do not give more than 3 days without explicit veterinary authorization.

It may interact with other NSAIDs, corticosteroids, ACE inhibitors, diuretics, and anticoagulants.

Side Effects and Safety

Common side effects include decreased appetite, vomiting, diarrhea, and lethargy. More serious side effects can occur, such as gastrointestinal ulceration, kidney damage, liver toxicity, and anemia.

Cautions · 12

When Onsior should be used with caution or avoided

Some cats should not take Onsior, 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 Onsior.

cats under 4 months or under 5.5 lbs
dehydrated cats
cats with kidney, liver, or heart disease
use with other NSAIDs or corticosteroids
cats with GI ulcers or bleeding disorders

Interactions · 13

Onsior drug interactions

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

other NSAIDs

corticosteroids

ACE inhibitors

diuretics

anticoagulants

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 Onsior, 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:

Vomiting or blood in stool
Loss of appetite
Lethargy or depression
Yellowing of gums or eyes
Decreased urination or dark urine

Frequently Asked Questions

Frequently Asked · 07

Questions about this medication

Is Onsior safe for cats?

Onsior is one of the very few NSAIDs FDA-approved for cats, and it is considered safe when used as directed. However, it is approved for a maximum of 3 consecutive days in cats. Cats are much more sensitive to NSAIDs than dogs, so strict adherence to the prescribed duration is critical.

Why can cats only take Onsior for 3 days?

Cats metabolize NSAIDs differently than dogs and are more susceptible to kidney and GI side effects. The 3-day limit is based on safety studies showing that longer use increases the risk of adverse effects. Some vets may prescribe longer courses in specific situations, but this requires close monitoring.

What pain medication is safe for cats?

Very few pain medications are safe for cats. Onsior (robenacoxib) is one of the only FDA-approved NSAIDs for cats (up to 3 days). Buprenorphine, gabapentin, and solensia (a monthly injection) are other options your vet may recommend. Never give cats human pain medications like ibuprofen or acetaminophen, which are toxic.

Can I give my cat Onsior after surgery?

Yes, Onsior is commonly prescribed for post-surgical pain management in cats, typically for up to 3 days. Your vet may also provide an injectable dose during surgery and then send you home with tablets for 1-3 days of follow-up pain management.

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 Onsior. It cannot decide whether this drug, indication, formulation, or schedule is appropriate for an individual animal.

Context in this medication record

Commonly listed uses: post-surgical pain, acute pain, inflammation, soft tissue surgery pain
Recorded forms: tablet, injectable
Reference timing: once daily (max 3 consecutive days for cats); onset 30-60 minutes; duration 24 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

cats under 4 months or under 5.5 lbs; dehydrated cats; cats with kidney, liver, or heart disease; use with other NSAIDs or corticosteroids; cats with GI ulcers or bleeding disorders.

Recorded interactions

other NSAIDs; corticosteroids; ACE inhibitors; diuretics; anticoagulants.

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.

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.

Plumb's Veterinary Drug Handbook — listed in this medication's source record.
Merck Veterinary Manual — listed in this medication's source record.
DailyMed label search for Robenacoxib — check current product and formulation labels; some veterinary uses may be off-label.

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 mg per kg (0.45 mg per lb) of body weight, given once daily (max 3 consecutive days for cats). 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

Pet Medication Safety Hub — What's safe, what's dangerous, and emergency signs
How we calculate dosages — Our sources, math, and review process
Printable emergency checklist — One-page reference for your fridge or first aid kit