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PetDosageChart

Onsior (Robenacoxib) Dosage for Cats

Non-steroidal anti-inflammatory drug (NSAID) ⏱ Onset: 30-60 minutes ⏳ Duration: 24 hours

This dosage information is for educational purposes only. Always consult your veterinarian before giving any medication to your pet. Dosages may vary based on your pet's health conditions, other medications, and individual factors.

Content reviewed by licensed veterinarians. This information is sourced from veterinary drug references including Plumb's Veterinary Drug Handbook and the Merck Veterinary Manual.

Dosage Calculator

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Onsior Dosage Chart for Cats by Weight

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Weight Low Dose Standard Dose Max Dose Frequency
3 lbs (1.4 kg) 1.5mg 1.5mg 3.5mg once daily (max 3 consecutive days for cats)
4 lbs (1.8 kg) 2mg 2mg 4.5mg (6mg tablet) once daily (max 3 consecutive days for cats)
5 lbs (2.3 kg) 2.5mg 2.5mg 5.5mg (6mg tablet) once daily (max 3 consecutive days for cats)
6 lbs (2.7 kg) 2.5mg 2.5mg 6.5mg (6mg tablet) once daily (max 3 consecutive days for cats)
7 lbs (3.2 kg) 3mg 3mg 7.5mg once daily (max 3 consecutive days for cats)
8 lbs (3.6 kg) 3.5mg 3.5mg 8.5mg once daily (max 3 consecutive days for cats)
9 lbs (4.1 kg) 4mg 4mg 10mg once daily (max 3 consecutive days for cats)
10 lbs (4.5 kg) 4.5mg (6mg tablet) 4.5mg (6mg tablet) 11mg (2 × 6mg) once daily (max 3 consecutive days for cats)
12 lbs (5.4 kg) 5.5mg (6mg tablet) 5.5mg (6mg tablet) 13mg (2 × 6mg) once daily (max 3 consecutive days for cats)
14 lbs (6.3 kg) 6.5mg (6mg tablet) 6.5mg (6mg tablet) 15mg once daily (max 3 consecutive days for cats)
16 lbs (7.3 kg) 7.5mg 7.5mg 17.5mg (3 × 6mg) once daily (max 3 consecutive days for cats)
18 lbs (8.2 kg) 8mg 8mg 19.5mg once daily (max 3 consecutive days for cats)
20 lbs (9.1 kg) 9mg 9mg 22mg once daily (max 3 consecutive days for cats)
25 lbs (11.3 kg) 11.5mg (2 × 6mg) 11.5mg (2 × 6mg) 27mg once daily (max 3 consecutive days for cats)

What is Onsior (Robenacoxib) used for in cats?

post-surgical pain acute pain inflammation soft tissue surgery pain

How to give Onsior 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.

Available Forms

tablet, injectable

Give with Food?

No — can be given without food

Side effects of Onsior in cats

Common side effects

decreased appetite
vomiting
diarrhea
lethargy

Serious side effects

  • gastrointestinal ulceration
  • kidney damage
  • liver toxicity
  • anemia

When to call the vet

Call your vet immediately if your cat shows any of these signs:

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

Related Medications for Cats

Nonsteroidal Anti-Inflammatory Drug (NSAID)

Metacam

Meloxicam

For Acute post-operative pain (single injection)

View dosage chart
Nonsteroidal Anti-Inflammatory Drug (NSAID) / Antiplatelet Agent

Bayer Aspirin

Aspirin (Acetylsalicylic Acid)

For Blood clot prevention (thromboembolism prophylaxis)

View dosage chart
Opioid Analgesic (Atypical)

Ultram

Tramadol

For Moderate to severe pain management

View dosage chart
Partial opioid agonist

Simbadol

Buprenorphine

For moderate pain relief

View dosage chart

Sources & References

The dosage information on this page is compiled from the following veterinary and pharmaceutical references:

  • Plumb's Veterinary Drug Handbook — the standard veterinary pharmacology reference used by veterinarians worldwide.
  • Merck Veterinary Manual — a trusted, peer-reviewed resource for veterinary professionals and pet owners.
  • DailyMed (FDA Drug Labels) — official FDA-approved drug labeling and prescribing information for Robenacoxib.

Frequently Asked Questions

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.

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