Onsior for Cats: Dosage, Safety & When Vets Prescribe It
3-Day Maximum FDA-Approved Use
Onsior (robenacoxib) is a COX-2 selective NSAID for short-term pain relief in cats. Costs $3-5 per tablet. Safer than many NSAIDs but limited to 3 days due to kidney/GI concerns.
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Onsior (robenacoxib) is an NSAID approved for short-term pain relief in cats. It's commonly used after surgery, dental procedures, or for acute injuries. Here's what cat owners need to know about this medication.
What Is Onsior?
Onsior contains robenacoxib, a newer-generation NSAID (non-steroidal anti-inflammatory drug) designed specifically for cats and dogs. It reduces pain and inflammation by targeting COX-2 enzymes while sparing COX-1 — theoretically reducing GI and kidney side effects.
Key Facts:
- • Generic name: Robenacoxib
- • Drug class: COX-2 selective NSAID
- • FDA approved: Yes, for cats (up to 3 days)
- • Forms: 6mg tablets, injectable solution
- • Cost: $3-5 per tablet
Common Uses for Onsior in Cats
- • Post-Surgical Pain: Spays, neuters, dental extractions, orthopedic surgery. Often given as injection at surgery, then tablets at home.
- • Acute Injuries: Falls, fights with other cats, sprains and strains. Short-term relief while injury heals.
- • Musculoskeletal Pain: Soft tissue inflammation. Not recommended for ongoing arthritis management due to 3-day limit.
Dosing Information
Important: Onsior is FDA-approved for cats for a maximum of 3 consecutive days. Do not exceed this without explicit veterinary direction.
Standard Dosing:
- • Dose: 1-2.4 mg/kg once daily
- • Cat tablet size: 6mg (sized for average cats)
- • Cats 2.5-6 kg (5.5-13 lbs): One 6mg tablet daily
- • Administration: Give on an empty stomach for best absorption
- • Duration: Up to 3 days maximum
Why the 3-Day Limit?
Cats metabolize drugs differently than dogs and humans. All NSAIDs carry kidney and GI risks in cats, and longer use significantly increases these risks. The 3-day limit reflects the FDA's safety determination based on clinical trials.
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Try VetLens FreeOnsior vs. Metacam: Comparison
Onsior (Robenacoxib)
- Selectivity: Highly COX-2 selective
- Duration: Max 3 days
- Form: Tablets, injection
- Cost: $3-5/tablet
- Best for: Short-term post-surgical pain
Metacam (Meloxicam)
- Selectivity: Preferentially COX-2
- Duration: Can be used longer (with monitoring)
- Form: Oral suspension, injection
- Cost: $30-50/bottle
- Best for: When longer treatment needed
For chronic arthritis pain, neither NSAID is ideal for cats. Consider Solensia (monthly injection) or gabapentin for long-term management.
Side Effects
Common Side Effects
Most cats tolerate short-term Onsior well. Watch for:
- • Decreased appetite
- • Vomiting
- • Soft stool or diarrhea
- • Lethargy (may also be from underlying condition/surgery)
Serious Side Effects (Rare with Short-Term Use)
Stop Onsior and contact your vet if you see:
- • Black, tarry stools (GI bleeding)
- • Bloody vomit
- • Severe vomiting or complete appetite loss
- • Yellowing of gums/eyes (liver issue)
- • Significant increase in drinking/urination (kidney issue)
- • Unusual bruising or bleeding
Who Should NOT Take Onsior
- • Cats under 4 months old or under 2.5 kg — Not safety-tested
- • Cats with kidney disease — All NSAIDs risk further kidney damage, especially in CKD cats
- • Dehydrated cats — Fix dehydration before any NSAID
- • Cats on other NSAIDs or steroids — Never combine; wait 5-7 days between switching
- • Cats with GI ulcers or bleeding disorders — NSAIDs increase bleeding risk
- • Pregnant or nursing cats — Safety not established
Drug Interactions
Tell your vet if your cat takes:
- • Corticosteroids (prednisolone) — Dramatically increases GI ulcer risk
- • Other NSAIDs (Metacam, aspirin) — Never combine
- • Diuretics (furosemide) — Both affect kidney function
- • Blood thinners — Increased bleeding risk
- • ACE inhibitors — Common in heart disease cats
Cost and Availability
- • Single tablet (6mg): $3-5
- • 3-day course: $9-15
- • Injection (at vet office): $15-30
Prescription required. Available at veterinary clinics and online pharmacies with valid Rx.
Related Reading
Track Your Cat's Pain Management
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- ✓ Log medication doses and timing
- ✓ Track recovery progress
- ✓ Monitor for side effects
- ✓ Share reports with your vet
Frequently Asked Questions
Is Onsior safe for cats with kidney disease?
Onsior has better kidney safety than many NSAIDs, but should still be used cautiously in cats with existing kidney disease. It's not recommended for cats with severe CKD (Stage 3-4). Always discuss kidney function with your vet.
Why can cats only take Onsior for 3 days?
The FDA approves Onsior for cats for up to 3 consecutive days to minimize kidney and GI side effects. Cats are more sensitive to NSAIDs than dogs. For chronic pain, Solensia is safer for long-term use.
Is Onsior better than Metacam for cats?
Both work well for cat pain. Onsior is more COX-2 selective and may have a slightly better safety profile, but the 3-day limit restricts its use. Metacam can be used longer but requires careful monitoring.
How much does Onsior cost for cats?
Onsior tablets cost approximately $3-5 per tablet. A 3-day course costs $9-15. It's only available by prescription.