Robenacoxib
5-ethyl-2-[(2,3,5,6-tetrafluorophenyl)amino]phenyl acetic acid
Also known as: Onsior · robenacoxibum · robénacoxib
Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Dosing by species
🌎 NA — North America🌍 EU — Europe
Dogs
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Pain and inflammation associated with chronic osteoarthritis | 1 mg/kg with a range of 1-2 mg/kg | PO | once daily | Discontinue after 10 days if no clinical improvement seen | 🌎 NA |
| Pain and inflammation associated with orthopedic or soft tissue surgery | 2 mg/kg | SC | once | — | 🌎 NA |
| Perioperative analgesia (orthopaedic and soft tissue surgery) | 2 mg/kg | SC | q24h | Maximum of 2 doses | 🌍 EU |
| Acute and chronic musculoskeletal disorders | 1-2 mg/kg | PO | q24h | Discontinue after 10 days if no clinical improvement | 🌍 EU |
- Pain and inflammation associated with chronic osteoarthritis: Give at the same time every day. For long term treatment, can adjust to lowest effective dose.
- Pain and inflammation associated with orthopedic or soft tissue surgery: Administer approximately 30 minutes before the start of surgery.
- Perioperative analgesia (orthopaedic and soft tissue surgery): Administer approximately 30 minutes before the start of surgery.
- Acute and chronic musculoskeletal disorders: Do not administer with food. Monitoring is recommended for long-term treatment (>12 weeks).
Cats
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Acute pain and inflammation associated with musculoskeletal disorders | 1 mg/kg; with a range of 1-2.4 mg/kg | PO | once daily | up to 6 days | 🌎 NA |
| Pain and inflammation associated with chronic osteoarthritis (Note: Label likely intended for surgical pain based on injection formulation) | 2 mg/kg | SC | once | — | 🌎 NA |
| Perioperative analgesia | 2 mg/kg | SC | q24h | Maximum of 2 doses | 🌍 EU |
| Acute and chronic musculoskeletal pain and inflammation | 1-2 mg/kg | PO | q24h | As directed by veterinarian | 🌍 EU |
- Acute pain and inflammation associated with musculoskeletal disorders: Equates to 1 tablet for cats weighing 2.5-<6 kg and 2 tablets for cats weighing 6 kg-<12 kg. Give either without food or with a small amount of food; tablets should not be divided or broken.
- Pain and inflammation associated with chronic osteoarthritis (Note: Label likely intended for surgical pain based on injection formulation): Administer approximately 30 minutes before the start of surgery.
- Perioperative analgesia: Administer approximately 30 minutes before the start of surgery.
- Acute and chronic musculoskeletal pain and inflammation: May be mixed with a small amount of food. Monitoring is recommended for long-term treatment (>12 weeks).
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Robenacoxib is a highly selective coxib-class non-steroidal anti-inflammatory drug (NSAID) licensed specifically for use in dogs and cats.
Key clinical features include:
- Tissue Selectivity: It exhibits a unique pharmacokinetic profile where it clears rapidly from the central blood compartment but persists at higher concentrations and for longer durations at sites of active inflammation (such as inflamed joints). This "tissue-sparing" effect helps maximize efficacy while minimizing systemic adverse effects.
- High COX-2 Specificity: It is approximately 140 times more selective for COX-2 in dogs and 500 times more selective in cats compared to COX-1, making it one of the most COX-2 specific NSAIDs available in veterinary medicine.
- Indications: Primarily used for the management of chronic osteoarthritis pain in dogs, acute musculoskeletal pain in cats, and perioperative pain associated with soft tissue or orthopedic surgeries in both species.
Mechanism of action
Robenacoxib exerts its anti-inflammatory and analgesic effects by selectively inhibiting the Cyclooxygenase-2 (COX-2) enzyme.
Arachidonic Acid → COX-2 Enzyme → Prostaglandin E2 (PGE2) and other inflammatory mediators.
By specifically targeting the inducible COX-2 isoform, robenacoxib effectively blunts the production of prostaglandins responsible for pain, inflammation, and fever. Because it largely spares the constitutive COX-1 enzyme, it preserves the homeostatic prostaglandins that are crucial for maintaining gastrointestinal mucosal integrity, renal blood flow, and normal platelet function.
Safety & warnings
Contraindications
- Patients with active gastrointestinal ulcers
- Hypersensitivity to robenacoxib or its excipients
- Dogs with hepatic disease
- Dehydrated, hypovolaemic, or hypotensive patients
- Patients with pre-existing gastrointestinal disease or ulceration
- Patients with blood clotting disorders
- Pregnant or lactating animals
- Dogs < 12 weeks of age or < 2.5 kg body weight
- Cats < 16 weeks of age or < 2.5 kg body weight
- Perioperative use in animals with renal disease (not advisable)
Adverse effects
- Decreased appetite
- Blood in feces (melena/hematochezia)
- Mild gastrointestinal signs (vomiting, soft feces, diarrhea)
- Gastrointestinal ulceration or bleeding (rare but severe)
- Renal toxicity (especially if hypotensive or dehydrated)
- Hepatic accumulation (in patients with pre-existing liver disease)
Precautions
Strict Veterinary Monitoring Required: Use with extreme caution in patients with impaired cardiac or renal function, dehydration, hypovolemia, hypotension, or in cats with hepatic dysfunction.
- Washout Period: Do not use concurrently with corticosteroids or other NSAIDs. A treatment-free period of at least 24 hours (accounting for the half-life of the previous drug) should be observed before starting robenacoxib.
- Renal Perfusion: Use cautiously with drugs that affect renal blood flow (e.g., diuretics, ACE inhibitors) due to the risk of renal toxicity.
- Reproduction: Safety has not been established in pregnant or lactating animals; use is not recommended.
Drug interactions
Some NSAIDs can reduce effects on blood pressure
May increase the risk of gastrointestinal toxicity (e.g., ulceration, bleeding, vomiting, diarrhea)
May increase the risk of gastrointestinal toxicity (e.g., ulceration, bleeding, vomiting, diarrhea)
NSAIDs may increase serum levels
Administration has increased plasma levels of celecoxib in humans and potentially could also affect robenacoxib levels in dogs
NSAIDs may reduce the saluretic and diuretic effects
As robenacoxib is highly bound to plasma proteins (>99%), it may displace other highly bound drugs or be displaced by them, potentially leading to increased serum levels and toxicity
Serious toxicity has occurred when NSAIDs have been used concomitantly; use together with extreme caution
May enhance the risk of nephrotoxicity development
Increased risk of severe gastrointestinal ulceration and renal toxicity. Require a 3-5 day wash-out period.
Increased risk of severe gastrointestinal ulceration and bleeding.
Increased risk of nephrotoxicity.
Monitoring
- Baseline and periodic physical examinations to assess clinical efficacy and adverse effects
- Baseline and periodic CBC, serum biochemistry (liver and renal function), electrolytes, and urinalysis
- For long-term therapy in dogs: Monitor liver enzymes at the start of therapy, and after 2, 4, and 8 weeks; then every 3-6 months
- Discontinue therapy if liver enzymes increase markedly or if accompanied by clinical signs (anorexia, apathy, vomiting)
- Clinical response (reduction in pain and inflammation)
- Gastrointestinal signs (monitor for vomiting, diarrhea, or melena)
- Renal parameters (BUN, Creatinine, USG) and hepatic enzymes, especially prior to anesthesia or during long-term therapy (>12 weeks)
Pharmacokinetics
Half-life
Absorption
Peak blood concentrations occur approximately 30 minutes after dosing in both dogs and cats. In dogs, food decreases peak levels somewhat. In cats, a small amount of food does not impact absorption.
Distribution
Highly bound to plasma proteins (>99%). Robenacoxib persists longer and at higher concentrations at sites of inflammation (e.g., inflamed joints) than in the central blood compartment.
Metabolism
Extensively metabolized by the liver in both dogs and cats. It does not appear to induce hepatic enzymes in dogs.
Elimination
In dogs, excretion is primarily biliary (~65%) with the remainder excreted renally. In cats, elimination is 70% biliary and 30% renal.
Overdose
Acute overdoses may potentially cause gastrointestinal, kidney, or liver toxicity.
Interestingly, chronic toxicity studies in healthy young dogs (up to 10 mg/kg/day for 6 months) and cats (up to 10 mg/kg SC for 3 days) did not produce signs of toxicity.
Treatment: If an acute overdose occurs, symptomatic and supportive therapy is recommended. This may include the administration of gastrointestinal protective agents (e.g., sucralfate, omeprazole), IV fluid therapy for forced diuresis and renal support, and contacting an animal poison control center for guided management.
Available products
Formulations
- Flavored oral tablets (canine and feline)
- Solution for injection
- 5 mg flavoured tablets (dogs)
- 10 mg flavoured tablets (dogs)
- 20 mg flavoured tablets (dogs)
- 40 mg flavoured tablets (dogs)
- 6 mg flavoured tablets (cats)
- 20 mg/ml injectable solution
Veterinary
- Robenacoxib Flavored Oral Tablets (dogs): 5 mg, 10 mg, 20 mg, 40 mg
- Robenacoxib Flavored Tablets (cats): 6 mg
- Robenacoxib Solution for Injection: 20 mg/mL in 20 mL multi-dose vials
- Onsior 5 mg flavoured tablets for dogs
- Onsior 10 mg flavoured tablets for dogs
- Onsior 20 mg flavoured tablets for dogs
- Onsior 40 mg flavoured tablets for dogs
- Onsior 6 mg flavoured tablets for cats
- Onsior 20 mg/ml solution for injection
Regulatory status
POM-V classification
POM-V classification
No regulatory data for: 🇺🇸 US · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Store canine flavored tablets at 25°C (77°F) or less. Store feline flavored tablets at no more than 30°C (86°F). The injection should be stored in the refrigerator (2°-8°C) in its original outer carton.
Client information
Onsior® (Robenacoxib) is a medication used to relieve pain and inflammation in your pet. To ensure it works safely and effectively, please follow these guidelines:
- For Dogs: Give the tablet on an empty stomach. Administer it at least 30 minutes before or after a meal.
- For Cats: You can give the tablet with or without a small amount of food. Do not divide, break, or crush the tablets.
- Handling: Wash your hands after handling the medication. Pregnant women who are near term should wear gloves when handling this drug.
- What to Watch For: Stop giving the medication and contact your veterinarian immediately if your pet shows any signs of illness, such as:
- Severe or bloody vomiting or diarrhea
- Loss of appetite or extreme lethargy (listlessness)
- Yellowing of the whites of the eyes or gums (jaundice)
- Collapse or weakness
- Never give your pet any other pain medications (like aspirin, ibuprofen, or other veterinary NSAIDs) or steroids while they are taking this drug without consulting your veterinarian.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.