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Onsior 6mg Tablets for Cats (pack of 30)

Onsior is used for the treatment of pain and inflammation associated with musculo-skeletal disorders in cats. It is also used for the reduction of moderate pain and inflammation associated with orthopaedic surgery in cats.
Brand Free Spirit
Manufacturer Elanco
Species Cat
Prescription Type POM-V (Written prescription required)
In stock

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Name: Onsior 6mg Tablets for Cats (pack of 30)

Description: Onsior is used for the treatment of pain and inflammation associated with musculo-skeletal disorders in cats. It is also used for the reduction of moderate pain and inflammation associated with orthopaedic surgery in cats.


What is Onsior and who is it for?


Onsior is a tablet that is used for the treatment of pain and inflammation associated with acute or chronic musculo-skeletal disorders in cats. It is also used for the reduction of moderate pain and inflammation associated with orthopaedic surgery in cats.


This is a Prescription only medicine (POM-V).

Onsior is only available with a prescription from your veterinary surgeon.

To check the most up to date information about this product, please read its Summary of Product Characteristics (SPC). It can be viewed here.


What is the active ingredient in Onsior?


Robenacoxib is a non-steroidal anti-inflammatory drug (NSAID) of the coxib class. It is a potent and selective inhibitor of the cyclooxygenase 2 enzyme (COX-2). The cyclooxygenase enzyme (COX) is present in two forms. COX-1 is the constitutive form of the enzyme and has protective functions, e.g. in the gastrointestinal tract and kidneys. COX-2 is the inducible form of the enzyme which is responsible for the production of mediators including PGE2 which induce pain, inflammation or fever.
In the in vitro whole blood assay in cats, the selectivity of robenacoxib was approximately 500 fold higher for COX-2 (IC50 0.058 μM) as compared to COX-1 (IC50 28.9 μM). At a dose of 1–2 mg/kg body weight, robenacoxib tablets produced a marked inhibition of COX-2 activity in cats and had no effect on COX-1 activity. In an inflammation model in cats, robenacoxib injection had analgesic, anti-inflammatory and anti-pyretic effects and a rapid onset of action (0.5 h). In clinical trials in cats, robenacoxib tablets reduced pain and inflammation associated with musculoskeletal disorders and reduced the need for rescue treatment when given as premedication in case of orthopaedic surgery, in combination with opioids. In two clinical trials in (mainly indoor) cats with chronic musculo-skeletal disorder, robenacoxib increased the activity and improved subjective scores of activity, behaviour, quality of life, temperament and happiness of the cats. Differences between robenacoxib and placebo were significant (P<0.05) for the client specific outcome measures, but did not reach significance (P=0.07) for the feline musculoskeletal pain index.
In a clinical study, 10 of 35 CMSD cats were assessed to be significantly more active when treated with robenacoxib for three weeks compared to these same cats when they received a placebo treatment. Two cats were more active when given placebo and for the remaining 23 cats no significant difference in activity could be detected between robenacoxib and placebo treatment.


How does it work?


Absorption: After oral administration of robenacoxib tablets at approximately 2 mg/kg without food, peak blood concentrations are attained rapidly with a Tmax of 0.5 h, a Cmax of 1,159 ng/ml and an AUC of 1,337 5 ng·h/ml. Co-administration of robenacoxib tablets with one third of the daily food ration produced no change in Tmax (0.5 h), Cmax (1,201 ng/ml) or AUC (1383 ng·h/ml). Co-administration of robenacoxib tablets with the entire daily food ration produced no delay in Tmax (0.5 h), but a lower Cmax (691 ng/ml) and a slightly lower AUC (1,069 ng·h/ml). The systemic bioavailability of robenacoxib tablets was 49% without food.

Distribution: Robenacoxib has a relatively small volume of distribution (Vss 190 ml/kg) and is highly bound to plasma proteins (more than 99%).

Biotransformation: In cats robenacoxib is extensively metabolised by the liver. Apart from one lactam metabolite, the identity of other metabolites is not known in cats.

Elimination: Robenacoxib is rapidly cleared from blood (CL 0.44 L/kg/h) with an elimination t1/2 of 1.1 h after intravenous administration. After oral administration of tablets, the terminal half-life from blood was 1.7 h. Robenacoxib persists longer and at higher concentrations at sites of inflammation than in blood. Robenacoxib is excreted predominantly via the biliary route (~70%) rather than via the kidneys (~30%). The pharmacokinetics of robenacoxib do not differ between male and female cats.


30 tablets


What is in Onsior?


Round, beige to brown tablets with the imprint "NA" on one side and the imprint "AK" on the other side.


Each tablet contains:

Active substances:

Robenacoxib 6 mg



Yeast powder

Cellulose, microcrystalline

Povidone (K-30)


Silica, colloidal anhydrous

Magnesium stearate


How do I use Onsior?


Onsior is a prescription product and must be used according to the instructions of your veterinary surgeon.

Please read the product leaflet thoroughly before administering to your pet.

Further advice

Is there any further advice I should know about Onsior?




Do not use in cats suffering from gastrointestinal ulceration.

Do not use concomitantly with corticosteroids or other non-steroidal anti-inflammatory drugs (NSAIDs).

Do not use in case of hypersensitivity to the active substance or to any of the excipients.

Do not use in pregnant and lactating animals.


Special precautions for use in animals


The safety of the veterinary medicinal product has not been established in cats weighing less than 2.5 kg or under 4 months of age.

Use in cats with impaired cardiac, renal or hepatic function or in cats that are dehydrated, hypovolaemic or hypotensive may involve additional risks. If use cannot be avoided, these cats require careful monitoring.

Response to long-term treatment should be monitored at regular intervals by a veterinary surgeon. Clinical field studies showed that robenacoxib was well-tolerated by most cat for up to 12 weeks.

Use this veterinary medicinal product under strict veterinary monitoring in cats with a risk of gastrointestinal ulcers, or if the cat previously displayed intolerance to other NSAIDs.


Special precautions to be taken by the person administering the product to animals


Wash hands after use of the veterinary medicinal product.

In small children, accidental ingestion increases the risk for NSAID adverse effects. In case of accidental ingestion, seek medical advice immediately and show the package leaflet or the label to the physician.

In pregnant women, particularly near term pregnant women, prolonged dermal exposure increases the risk for premature closure of the ductus arteriosus in the foetus.


Adverse reactions


Mild and transient diarrhoea, soft faeces or vomiting were commonly reported in clinical trials with treatment up to 6 days. In very rare cases, lethargy may be observed.

Vomiting was very commonly reported, and anorexia, diarrhoea, lethargy and inappropriate defecation were commonly reported in field studies with treatment up to 12 weeks in cats with chronic musculo-skeletal disorder, with similar frequencies in the Onsior and placebo treated cats.

The frequency of adverse reactions is defined using the following convention:

- very common (more than 1 in 10 animals displaying adverse reaction(s) during the course of one treatment)

- common (more than 1 but less than 10 animals in 100 animals)

- uncommon (more than 1 but less than 10 animals in 1,000 animals)

- rare (more than 1 but less than 10 animals in 10,000 animals)

- very rare (less than 1 animal in 10,000 animals, including isolated reports).


Use during pregnancy and lactation


Do not use in pregnant and lactating animals because the safety of robenacoxib has not been established during pregnancy and lactation or in cats used for breeding.


Interaction with other medicinal products and other forms of interaction


Onsior must not be administered in conjunction with other NSAIDs or glucocorticosteroids. Pre-treatment with other anti-inflammatory medicines may result in additional or increased adverse effects and, accordingly, a treatment-free period with such substances should be observed for at least 24 hours before the commencement of treatment with Onsior. The treatment-free period, however, should take into account the pharmacokinetic properties of the products used previously.

Concomitant treatment with medicines displaying action on renal flow, e.g. diuretics or angiotensin converting enzyme (ACE) inhibitors, should be subject to clinical monitoring. In healthy cats treated with or without the diuretic furosemide, concomitant administration of Onsior with the ACE inhibitor benazepril for 7 days was not associated with any negative effects on plasma aldosterone concentrations, plasma renin activity or glomerular filtration rate. No safety data in the target population and no efficacy data in general exist for the combined treatment of robenacoxib and benazepril.

As anaesthetics may affect renal perfusion, the use of parenteral fluid therapy during surgery should be considered to decrease potential renal complications when using NSAIDs peri-operatively.

Concurrent administration of potentially nephrotoxic medicines should be avoided as there might be an increased risk of renal toxicity.

Concurrent use of other active substances that have a high degree of protein binding may compete with robenacoxib for binding and thus lead to toxic effects.


Overdose (symptoms, emergency procedures, antidotes), if necessary


In healthy young cats aged 7–8 months, oral robenacoxib administered at high overdoses (4, 12 or 20 mg/kg/day for 6 weeks) did not produce any signs of toxicity, including no evidence of any gastrointestinal, kidney or liver toxicity and no effect on bleeding time.

In healthy young cats aged 7- 8 months, oral robenacoxib (Onsior tablets) administered at overdoses of up to 5 times the maximum recommended dose (2.4 mg, 7.2 mg, 12 mg robenacoxib/kg bodyweight ) for 6 months was well tolerated. A reduction in body weight gain was observed in treated animals. In the high dose group kidney weights were decreased and sporadically associated with renal tubular degeneration/ regeneration but not correlated with evidence of renal dysfunction on clinical pathology parameters.

The interchangeable use of Onsior tablets and Onsior solution for injection in 4-months old cats at overdoses of up to 3 times the maximum recommended dose (2.4 mg, 4.8 mg, 7.2 mg robenacoxib/kg orally and 2.0 mg, 4.0 mg and 6.0 mg robenacoxib/kg subcutaneously) resulted in a dose-dependent increase of sporadic oedema at the injection site and minimal to mild subacute/chronic inflammation of the subcutaneous tissue. A dose-dependent increase in the QT interval, a decreased heart rate and corresponding increased respiratory rate were observed in laboratory studies. No relevant effects on body weight, bleeding time or evidence of any gastrointestinal, kidney or liver toxicity were observed.

In overdose studies conducted in cats, there was a dose-dependent increase in the QT interval. The biological relevance of increased QT intervals outside of normal variations observed following overdose of robenacoxib is unknown. No changes in the QT interval were observed after single intravenous administration of 2 or 4 mg /kg robenacoxib to anaesthetised healthy cats.

As with any NSAID, overdose may cause gastrointestinal, kidney, or liver toxicity in sensitive or compromised cats. There is no specific antidote. Symptomatic supportive therapy is recommended and should consist of administration of gastrointestinal protective agents and infusion of isotonic saline.


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