Onsior (robenacoxib) Inj 20mg per mL/ 20 mL multidose vial - For Cats Only | On Sale | EntirelyPets Rx
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Onsior (robenacoxib) Inj 20mg per mL/ 20 mL multidose vial - For Cats Only Video

Onsior (robenacoxib) Inj 20mg per mL/ 20 mL multidose vial - For Cats Only

Item# IWM060950
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Onsior or Robenacoxib is a nonsteroidal anti-inflammatory drug [NSAID] that effectively relieves acute pain and post soft-tissue surgery and inflammation in cats. It travels rapidly through the bloodstream to selectively target the tissues involved in inflammation and pain. The drug takes effect and exits the blood quickly, to reduce potential side effects. Causes fewer gastrointestinal side effects by selective inhibition of prostaglandin formation.

Key Benefits

  • is ideal for spays and neuters
  • is rapidly absorbed and persists at the site of inflammation*1
  • gives veterinarians the flexibility to transition a surgical patient from Onsior injection to sending home Onsior® (robenacoxib) Tablets for Cats

How it works

Onsior contains the active ingredient robenacoxib, an NSAID (non-steroidal anti-inflammatory drug) that targets the COX-2 enzyme that causes pain. It spares the COX-1 enzyme to protect your pet's gastrointestinal tract and blood platelet functions. The tablet is quickly absorbed from the gastrointestinal tract and is effective for 24 hours.


Onsior® (robenacoxib) injection is indicated for the control of postoperative pain and inflammation associated with orthopedic surgery, ovariohysterectomy and castration in cats ≥ 4 months of age; for up to a maximum of 3 days.

Onsior® (robenacoxib) Tablets for Cats are indicated for the control of postoperative pain and inflammation associated with orthopedic surgery, ovariohysterectomy and castration in cats ≥ 5.5 lbs (2.5 kg) and ≥ 4 months of age; for up to a maximum of 3 days.


View Onsior Injection Drug Facts Sheet.

Carefully consider the potential benefits and risks of Onsior and other treatment options before deciding to use Onsior (robenacoxib) injection. Use the lowest effective dose for the shortest duration consistent with individual response. It is recommended as good aseptic practice to clean stopper surface with isopropyl alcohol before and after each insertion of a needle.

The dose of Onsior (robenacoxib) injection is 0.91 mg/lb (2 mg/kg) subcutaneously once daily, for a maximum of 3 days.

Dosage Directions

For subcutaneous injection in cats ≥ 4 months of age; for up to a maximum of 3 days. To ensure accuracy of dosing, the use of a 1 mL graduated syringe is recommended. The first dose should be administered approximately 30 minutes prior to surgery, at the same time as the pre-anesthetic agents are given.

Subsequent doses can be given via subcutaneous injection, or interchanged with the oral tablet in cats ≥ 5.5 lbs and ≥ 4 months of age, for a maximum of 3 total Onsior doses over 3 days, not to exceed one dose per day (see Animal Safety and Onsior tablet product insert).

Note: In cats, the dose of Onsior tablets and Onsior injection are different.


Federal (USA) law restricts this drug to use by or on the order of a licensed veterinarian.Description:


Onsior (robenacoxib) injection should not be used in cats that have a hypersensitivity to robenacoxib or known intolerance to NSAIDs.


Not for use in humans. Keep this and all medications out of reach of children. Consult a physician in case of accidental ingestion or injection by humans. For subcutaneous use in cats and dogs (see reverse side for instructions for use in dogs).

All cats should undergo a thorough history and physical examination before the initiation of NSAID therapy. Appropriate laboratory tests should be conducted to establish hematological and serum biochemical baseline data prior to administration of an NSAID. Owners should be advised to observe for signs of potential drug toxicity (see Adverse Reactions and Animal Safety).

Do not administer Onsior injection or tablets in conjunction with any other oral or injectable NSAID or corticosteroid.


When using NSAIDS such as Onsior, the use of fluid therapy during surgery is recommended to decrease potential renal complications (see Adverse Reactions, Post-Approval Experience).

Appetite should be monitored in cats receiving Onsior.

Stop administration of Onsior if appetite decreases or if the cat becomes lethargic. Inflammation at the injection site may be noted.

The use of Onsior has not been evaluated in cats younger than 4 months of age and less than 5.5 lbs, cats used for breeding, or in pregnant or lactating cats. Long-term use of the injectable has not been studied. Safety has not been demonstrated for IV or IM administration.The use of Onsior in cats with cardiac disease has not been studied. Onsior has been shown to prolong the QT interval.

As a class, cyclo-oxygenase inhibitory NSAIDs may be associated with gastrointestinal, renal, and hepatic toxicity. Sensitivity to drug-associated adverse events varies with the individual patient. Cats that have experienced adverse reactions from one NSAID may experience adverse reactions from another NSAID. Patients at greatest risk for adverse events are those that are dehydrated, on concomitant diuretic therapy, or those with existing renal, cardiovascular, and/or hepatic dysfunction. Anesthetic drugs may affect renal perfusion; approach concomitant use of anesthetics and NSAIDs cautiously.

Appropriate monitoring procedures (including ECG, blood pressure, and temperature regulation) should be employed during all surgical procedures. The use of parenteral fluids during surgery is recommended to decrease potential renal complications when using NSAIDs perioperatively.

If additional pain medication is needed after a daily dose of Onsior, a non-NSAID/non-corticosteroid class of analgesic may be necessary. Concurrent administration of potentially nephrotoxic drugs should be carefully approached and monitored. NSAIDs may inhibit prostaglandins which maintain normal homeostatic function. Such anti-prostaglandin effects may result in clinically significant disease in patients with underlying or pre-existing disease that has not been previously diagnosed. NSAIDs possess the potential to produce gastrointestinal ulcerations and/or gastrointestinal perforations. Do not use Onsior concomitantly with other anti-inflammatory drugs, such as NSAIDs or corticosteroids. Consider appropriate washout times when switching from one NSAID to another or when switching from corticosteroid use to NSAID use. Onsior injection and Onsior tablets are safe to use interchangeably when given once a day for a maximum of 3 days in cats ≥ 4 months of age and ≥ 5.5 lbs. Note: In cats, the dose of Onsior tablets and Onsior injection are different.

The use of concomitantly protein-bound drugs with Onsior has not been studied in cats. Commonly used protein-bound drugs include cardiac, anticonvulsant and behavioral medications. The influence of concomitant drugs that may inhibit metabolism of Onsior has not been evaluated. Drug compatibility should be monitored in patients requiring adjunctive therapy. Concurrent medications used during the field study with Onsior included parasiticides, anesthetics, pre-anesthetic medications, and antibiotics.

The effect of cyclo-oxygenase inhibition and the potential for thromboembolic occurrence or a hypercoagulable state has not been evaluated. It is unknown whether cats with a history of hypersensitivity to ß lactam drugs will exhibit hypersensitivity to Onsior. Robenacoxib is poorly soluble in water and in acid solutions readily degrades to form ?-lactam. In cats, lactam is a metabolite of robenacoxib. Additionally, lactam is a degradation product that increases over the shelf-life of the solution. Neurologic signs have been associated with the use of ß lactam drugs; it is unknown if the lactam in robenacoxib may cause similar neurologic signs (see Animal Safety). Occurrences of skin lesions/urticaria, seizures, ataxia, and nystagmus have been associated with the use of Onsior.

Robenacoxib may prolong the QT interval; the associated risk of developing ventricular arrhythmia is unknown. The use of robenacoxib with other drugs shown to prolong the QT interval is not recommended. Commonly used drugs that prolong the QT interval include antihistamines, prokinetic, and certain anesthetic drugs. Onsior (robenacoxib) injection contains sodium metabisulfite. Onsior (robenacoxib) injection should not be used in patients with sulfite hypersensitivity. As a class, it is unknown if the use of NSAIDs in asthmatic cats can cause acute asthmatic exacerbations, as seen in some humans.

Information for Cat Owners:

Onsior, like other drugs of its class, is not free from adverse reactions. Owners should be advised of the potential for adverse reactions and be informed of the clinical signs associated with drug intolerance.

Adverse reactions may include vomiting, diarrhea, decreased appetite, dark or tarry stools, increased water consumption, increased urination, anemia, yellowing of gums, skin or white of the eye due to jaundice, lethargy, incoordination, seizure, or behavioral changes. Serious adverse reactions associated with this drug class can occur without warning and result in death (see Warnings and Adverse Reactions). Owners should be advised to contact their veterinarian immediately if signs of intolerance are observed. The vast majority of patients with drug related adverse reactions have recovered when the signs are recognized, the drug is withdrawn, and veterinary care, if appropriate, is initiated.


Effectiveness was demonstrated using Onsior (robenacoxib) injection in a masked, placebo-controlled, multi-site field study involving client-owned cats. In this study, 349 cats presenting for ovariohysterectomy or castration in conjunction with an onychectomy (forelimbs only) were randomly administered Onsior injection or saline. Drug was administered approximately 30 minutes prior to surgery along with pre-anesthetic medications and continued once daily for two additional treatments. Effectiveness was evaluated in 348 cats (173 treated and 175 controls) and field safety was evaluated in 349 cats. A statistically significant difference in the proportion of treatment successes in the Onsior injection treatment group (83.5%) compared to the control group (61.9%) was observed. Statistically significant differences for pain elicited on palpation at the spay or castration incision site, paw pain, behavior following social interaction and from a distance, posture score and overall pain at various post-surgical time points were also observed. The results of the field study demonstrate that Onsior (robenacoxib) injection when administered for a maximum of 3 days is effective and well-tolerated for the control of postoperative pain associated with onychectomy, ovariohysterectomy, and castration in cats.


Store under refrigerated conditions 2°-8°C (36° - 46°F).Use within 12 weeks of first puncture.

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