This product requires a prescription from your veterinary surgeon. click here

Onsior 20mg Tablets for Dogs (pack of 30)

Onsior is used for the management of pain and inflammation associated with chronic osteoarthritis in dogs.
Brand Free Spirit
Manufacturer Elanco
Species Dog
Prescription Type POM-V (Written prescription required)
In stock

Prescription Medicine

You have just added a prescription medicine to your basket!

Before we can send out your pet's medication we will need a valid prescription from your veterinary surgeon.

If you already have a valid prescription for this medication saved on your pet’s record, then we'll be able to dispense this item immediately.

Name: Onsior 20mg Tablets for Dogs (pack of 30)

Description: Onsior is used for the management of pain and inflammation associated with chronic osteoarthritis in dogs.


What is Onsior and who is it for?


Onsior is a tablet that is used for the management of pain and inflammation associated with chronic osteoarthritis in dogs.


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 and is responsible for the production of mediators including PGE2 which induce pain, inflammation or fever.


In an in vitro whole blood assay in dogs, robenacoxib was approximately 140 fold selective for COX-2 (IC50 0.04 μM) as compared to COX-1 (IC50 7.9 μM). Robenacoxib produced marked inhibition of COX-2 activity and had no effect on COX-1 activity in dogs at oral doses ranging from 0.5 to 4 mg/kg. Robenacoxib tablets are therefore COX-1 sparing at recommended doses in dogs. Robenacoxib had analgesic and anti-inflammatory actions in an inflammation model in dogs with single oral doses ranging from 0.5 to 8 mg/kg, with an ID50 of 0.8 mg/kg and a rapid onset of action (0.5 h). In clinical trials robenacoxib tablets reduced the lameness and inflammation of dogs with chronic osteoarthritis.


How does it work?


Absorption: After oral administration of robenacoxib flavoured tablets at 1 mg/kg without food, peak blood concentrations are attained rapidly with a Tmax of 0.5 h, a Cmax of 1,124 ng/ml and an AUC of 1,249 ng·h/ml. Co-administration of robenacoxib non-flavoured tablets with food produced no delay in Tmax, but slightly lower values for Cmax (832 ng/ml) and AUC (782 ng·h/ml). The systemic bioavailability of robenacoxib tablets in dogs was 62% with food and 84% without food.

Distribution: Robenacoxib has a relatively small volume of distribution (Vss 240 ml/kg) and is highly bound to plasma proteins (>99%).

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

Elimination: Robenacoxib is cleared rapidly from blood (CL 0.81 L/kg/h) with an elimination t1/2 of 0.7 h after intravenous administration. After oral administration of the tablets, the terminal half-life in blood was 1.2 h. Robenacoxib persists longer and at higher concentrations at sites of inflammation than in blood. Robenacoxib is excreted predominantly via the biliary route (around 65%) and the remainder via the kidneys. Repeated oral administration of robenacoxib to dogs at dosages of 2–10 mg/kg for 6 months produced no change in the blood profile, with neither accumulation of robenacoxib nor enzyme induction. Accumulation of metabolites has not been tested. The pharmacokinetics of robenacoxib do not differ between male and female dogs, and are linear over the range 0.5–8 mg/kg.


30 tablets


What is in Onsior?


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


Each tablet contains:

Active substances:

Robenacoxib 20 mg



Yeast powder

Cellulose, microcrystalline

Flavour, artificial beef

Cellulose, powdered

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 dogs suffering from gastrointestinal ulceration or with hepatic disease. 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 (see section below).


Special warnings for each target species


In clinical studies, inadequate response to treatment was seen in 10–15% of the dogs.


Special precautions for use in animals


The safety of the veterinary medicinal product has not been established in dogs weighing less than 2.5 kg or under 3 months of age. For long term therapy, liver enzymes should be monitored at the start of therapy, e.g. after 2, 4 and 8 weeks. Thereafter it is recommended to continue regular monitoring, e.g. every 3–6 months. Therapy should be discontinued if liver enzyme activities increase markedly or the dog shows clinical signs such as anorexia, apathy or vomiting in combination with elevated liver enzymes. Use in dogs with impaired cardiac or renal function or dogs that are dehydrated, hypovolaemic or hypotensive may involve additional risks. If use cannot be avoided, these dogs require careful monitoring. Use this product under strict veterinary monitoring in dogs with a risk of gastrointestinal ulcers, or if the dog 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 case of accidental ingestion, seek medical advice immediately and show the package leaflet or the label to the physician. In small children, accidental ingestion increases the risk for NSAID adverse effects. For pregnant women, particularly near term pregnant women, prolonged dermal exposure increases the risk of premature closure of the ductus arteriosus in the foetus.


Adverse reactions


Gastrointestinal adverse events were reported very commonly, but most cases were mild and recovered without treatment. Vomiting and soft faeces were very common, decreased appetite and diarrhoea were common, and blood in the faeces was uncommon. In dogs treated up to 2 weeks no increases in liver enzyme activities were observed. However, with long-term treatment, increases in liver enzyme activities were common. In most cases there were no clinical signs and the liver enzyme activities either stabilised or decreased with continued treatment. Increases in liver enzyme activities associated with clinical signs of anorexia, apathy or vomiting were uncommon. In very rare cases, lethargy may be observed.

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 or lactating dogs because the safety of robenacoxib has not been established during pregnancy and lactation or in dogs used for breeding.


Interaction with other medicinal products and other forms of interaction


Onsior must not be administered in conjunction with other NSAIDs. 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. 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 dogs aged 5–6 months, oral robenacoxib administered at high overdoses (4, 6 or 10 mg/kg/day for 6 months) did not produce any signs of toxicity, including no evidence of any gastrointestinal, kidney or liver toxicity and no effect on bleeding time. Robenacoxib also had no detrimental effects on cartilages or joints. As with any NSAID, overdose may cause gastrointestinal, kidney, or liver toxicity in sensitive or compromised dogs. There is no specific antidote. Symptomatic, supportive therapy is recommended consisting of administration of gastrointestinal protective agents and infusion of isotonic saline.


Write Your Own Review
Only registered users can write reviews. Please Sign in or create an account