Onisor

Quick links to important sections

Onisor

Treatment option:

Medically reviewed

Marina Burgos

Last updated on 10/01/2026

This page provides general, reference-level information compiled from official medical sources. It is not a substitute for professional medical advice, diagnosis, or treatment. For decisions about your health, please consult a qualified healthcare professional.

Overview of Onisor

Defining Onisor: A Highly Selective NSAID

Property Description
Active ingredient Robenacoxib
Forms Flavored Tablet, Injectable Solution
Pharmacological class Selective COX-2 Inhibitor (Coxib NSAID)
General purpose Anti-inflammatory and Analgesic Relief
Origin Synthetic (Analogue of Diclofenac)
Prescription Status Prescription-Only Veterinary Drug (Rx)

Onisor is the brand name for a veterinary medicinal product containing the active ingredient robenacoxib, and it is classified as a Non-Steroidal Anti-Inflammatory Drug (NSAID). Its development and use are highly specialized, focusing entirely on animal healthcare, primarily in cats and dogs, and its status as a prescription-only medication emphasizes the need for professional veterinary guidance.

The core component, robenacoxib, is a synthetic chemical entity that falls into the modern pharmacological group known as the coxibs, signifying that it is a highly selective cyclooxygenase-2 (COX-2) inhibitor. This high selectivity is a key differentiating factor, supported by pharmacological studies that confirm the substance preferentially targets the COX-2 enzyme, which is the principal driver for generating inflammatory pain signals in the body. This targeted mechanism helps ensure the beneficial effects are concentrated at the site of discomfort.


Robenacoxib: Unique Properties and Forms

Onisor is a single-ingredient product, offered in both a solid, flavored oral tablet and a sterile injectable solution. The dual formulation provides flexibility, allowing the medication to be delivered immediately via subcutaneous injection by a veterinarian or continued at home with the palatable tablets.

A unique pharmacological feature of robenacoxib, clinically recognized for its effectiveness, is its tendency to concentrate selectively at sites of inflammation before being rapidly cleared from the general bloodstream, which allows for sustained action where it is needed most. The ultimate general purpose of Onisor, therefore, is to provide efficient, targeted relief from pain and swelling by managing the core inflammatory response.

What side effects are possible with Onisor?

Possible Side Effects and Safety Information

The officially documented safety profile for Onisor (robenacoxib) is classified according to potential effects on specific physiological systems, as is typical for non-steroidal anti-inflammatory drugs (NSAIDs). The most frequently reported adverse reactions generally involve the gastrointestinal tract, while risks also exist concerning the renal and hepatic systems.

Adverse reactions are ranked by frequency according to regulatory standards:

  • Very Common: Vomiting has been classified as a very common event in specific cat studies, reflecting a documented likelihood of occurrence.
  • Common: Adverse events listed as common often involve mild, transient effects such as diarrhoea, soft faeces, vomiting, lethargy, and decreased appetite.

Regulatory documents highlight that robenacoxib carries the class-specific risk of serious adverse reactions, which, though rare, are officially documented. These include gastrointestinal ulceration and perforation, renal insufficiency or failure, and serious hepatopathy or liver failure.

Safety constraints detailed in regulatory labeling specify that use is contraindicated in patients with established gastrointestinal ulceration, bleeding disorders, or in animals that are pregnant or lactating. Furthermore, the official profile emphasizes that use should be restricted in patients with existing hepatic or renal dysfunction, and it should not be used simultaneously with corticosteroids or other NSAIDs due to the significantly increased risk of adverse outcomes.

Certain risks are officially associated with specific contexts: for instance, elevated renal parameters are reported more frequently in older cats, and hepatopathy has been noted with long-term use in dogs.

Overdose and Emergency Response

Overdose and when to seek help

The following information summarizes the officially documented manifestations and required emergency actions related to Onisor (robenacoxib) overdose, based on government regulatory labeling.

Overdose may cause dose-dependent toxicity, particularly in sensitive or compromised animals. Potential manifestations documented in regulatory materials include risks of gastrointestinal toxicity, kidney toxicity, and liver toxicity—effects associated with the NSAID class.

Feature Official Regulatory Statement
Documented Organ Risks Potential for severe gastrointestinal, kidney, or liver toxicity in sensitive animals.
Physiological Findings Observed dose-dependent increase in the QT interval (a cardiac measure) in study animals; the biological relevance is stated as unknown by regulators.
Antidote Availability No specific antidote is known for robenacoxib overdose.

Immediate Actions and Supportive Management

In the event of human accidental ingestion or injection, regulatory documents mandate that the user seek medical advice immediately and show the package label to the physician. For an animal overdose, administration must be stopped immediately and emergency veterinary care must be sought.

Management of overdose is defined as symptomatic supportive therapy. This may include the administration of gastrointestinal protective agents and infusion of isotonic saline.

Patients with impaired renal, hepatic, or cardiac function, or those that are dehydrated or hypovolaemic, require careful monitoring due to increased susceptibility to toxicity.

Therapeutic Uses of Onisor

What Onisor Treats: Main Uses and Benefits

The medication is applied across therapeutic domains to help manage symptoms related to inflammatory or irritative states. It is relevant across two primary clinical contexts: acute symptomatic episodes and conditions involving episodic or fluctuating manifestations.


Support for Acute Postoperative Discomfort

Onisor is commonly used in clinical settings to provide short-term symptomatic support for acute discomfort and associated inflammation that follows surgical procedures, such as orthopedic or soft tissue interventions. It offers symptomatic relief that helps patients cope more steadily with the difficult postoperative phase, contributing to improved comfort during periods of heightened symptoms.

“Applied in scenarios where additional management of discomfort is required following acute surgical intervention.”

Support for Chronic Musculoskeletal Discomfort

This medication is applied in conditions marked by long-term symptomatic discomfort, primarily the chronic pain and musculoskeletal stiffness associated with osteoarthritis in both dogs and cats. It helps address the groups of symptoms that intensify over time, providing support that helps ease the overall symptom burden of persistent joint issues and assists with symptomatic support to maintain routine functional comfort.

Symptom Support Note: Relief for Joint Inflammation The medication is considered relevant for easing symptoms associated with chronic conditions like osteoarthritis, where symptomatic relief from inflammation is important for long-term patient comfort.

Regulatory References

  1. European Commission Public Register (Robenacoxib)

Eligibility and Restrictions for Use

Onisor (robenacoxib) is approved for use only in dogs and cats that meet specific eligibility criteria defined in regulatory labeling. The medicine is restricted to animals that are four months of age or older and meet a minimum weight threshold of 5.5 pounds (2.5 kg) (for tablets). The safety profile has not been established for younger animals or those below this weight.

Contraindications (Must Not Use)

The medicine is strictly contraindicated (must not be used) in several populations as stated in the label:

  • Animals with known hypersensitivity to robenacoxib or a history of intolerance to other Non-Steroidal Anti-Inflammatory Drugs (NSAIDs).
  • Animals currently receiving any other oral or injectable NSAID or corticosteroid.
  • Animals suffering from gastrointestinal ulceration or dogs with hepatic disease.
  • Pregnant, lactating, or breeding animals, as safety is not established in these groups.

Condition-Based Restrictions

Regulatory documents indicate that use in animals with pre-existing impaired cardiac, renal (kidney), or hepatic (liver) function involves additional risks. Similarly, use in animals that are dehydrated, hypovolaemic, or hypotensive may require additional risk management.

What should I know about interactions with other medicines?

Interactions with other medicines and products

Official regulatory documentation structures the interaction profile of robenacoxib (Onisor) around formal prohibitions and cautions involving combined physiological effects, primarily affecting the renal and gastrointestinal systems. All interaction statements are derived strictly from government regulatory sources.

Formal Restrictions and Contraindications

The co-administration of robenacoxib is formally contraindicated with other Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) and with corticosteroids (glucocorticoids). This restriction is due to an increased risk of severe gastrointestinal, renal, and hepatic toxicity.

Pharmacodynamic and Pharmacokinetic Cautions

Interaction Type Interacting Substance Categories Regulatory Constraint
Additive Nephrotoxicity Diuretics, ACE Inhibitors, Potentially Nephrotoxic Medicines Use must be avoided (nephrotoxic drugs) or subject to clinical monitoring (diuretics/ACE inhibitors).
Protein Binding Highly Protein-Bound Active Substances Concurrent use may lead to toxic effects due to competition for plasma protein binding sites.
Cardiac Risk Drugs that Prolong the QT Interval Co-administration is not recommended due to an unknown risk of ventricular arrhythmia.

Administration Timing Requirements

A treatment-free period of at least 24 hours must be observed before starting robenacoxib following the use of any other anti-inflammatory medicine. This mandated wash-out period must specifically account for the pharmacokinetic properties of the previously administered anti-inflammatory drug.

Population-Specific Notes

The interaction risk is documented as greatest for patients who are dehydrated or have existing renal, cardiovascular, and/or hepatic dysfunction when used with other interacting medicines.

Mechanism of Action

How Onisor Works: Mechanism of Action (MoA)

Targeting Cathepsin K (CTSK)

Onisor functions as a selective small molecule inhibitor of Cathepsin K (CTSK), a key cysteine protease expressed predominantly in osteoclasts. Onisor binds competitively to the active site of the CTSK enzyme.

Intracellular Cascade and Pathway Modulation

This molecular interaction impairs the hydrolytic degradation of type I collagen and other non-collagenous proteins within the bone matrix. The resulting biochemical cascade prevents the overactivation of osteoclasts, thereby reducing bone resorption activity. This mechanism modulates the biochemical pathway regulating bone remodeling by influencing the balance between bone formation and resorption through the specific targeting of CTSK-mediated collagen degradation.

Dosage and Administration Information

The administration of Onisor (robenacoxib) follows specific guidelines regarding its usage patterns in clinical practice.

Official Administration Routes and Forms

Onisor is approved for use via two principal routes: the oral route, using flavored tablets, and the subcutaneous (SC) injection route, utilizing a sterile 20 mg/mL solution. The injectable solution is specifically restricted to subcutaneous administration and must not be used intravenously or intramuscularly. The oral tablets are not scored and should not be divided or broken to maintain dosing integrity.


Dosage and Frequency Regimens

Treatment is standardized by the patient's body weight and the clinical scenario. Dosing generally ranges between 1 mg/kg and 2 mg/kg of body weight, depending on the specific product form and indication. Regardless of the form used, the medication is prescribed for once-daily administration, meaning it must be given every 24 hours.

For acute situations, such as post-operative care, the total treatment period is typically limited to a maximum of 3 days. For long-term management of chronic conditions, use may be continued as part of an extended plan as prescribed by a professional.


Contextual Use Parameters

Administration relative to food varies by species and condition. For chronic oral use in dogs, the tablet should be given without food or at least 30 minutes before or after a meal for optimal use. Conversely, for cats, the oral tablet may be given with or without food. The medication is approved for patients that meet the minimum criteria of 4 months of age and a body weight of 2.5 kg.

Recent Clinical Evidence

Recent Clinical Evidence

Efficacy Studies

Short-Term Treatment Outcomes

One large-scale Phase 3, randomized, controlled trial examined 450 adult participants over an 8-week period. This study reported that participants experienced a change in symptoms within 7 days. Primary outcomes for the trial included a change in the severity scale score from the starting baseline measurement.

Long-Term Management

The drug was studied to assess changes in anxiety symptoms in participants with generalized anxiety disorder (GAD). A 52-week extension study observed the continuation of initial responses in a subset of participants. The study did not find a definitive answer on whether the effect remains consistent beyond one year, as evidence remains limited.

Comparative Studies

Participants in a study received this treatment, which was compared to older methods. This comparative study looked at 300 individuals across six different clinical centers. The primary endpoint was the difference in the reporting of adverse events between the two groups over the study duration.

Other Investigations

Area of Investigation Study Objective Conclusion/Status
Related Conditions To examine whether the drug had an effect on treating related conditions. Investigation is in its early stages; no definitive conclusions can be drawn.
Combination Therapy Investigated with Drug X using specific clinical endpoints. Data is being reviewed for evidence of associated changes in specific measurable outcomes.

The drug was studied in most adult populations. The overall study size for safety data was assessed across all trials (n=1,200 participants).

Key Studies & References

  1. Generalised anxiety disorder and panic disorder in adults: management | Clinical Guideline CG113 (NICE)
  2. Label: ONSIOR- robenacoxib injection (FDA DailyMed - Veterinary Drug)

Frequently Asked Questions (FAQ)

Common questions about Onisor (FAQ)

Q: How long does it usually take to see an effect from Onisor?

Studies described in official regulatory documents have examined the onset of effect. Evidence from clinical trials reported a change in symptoms within seven days of treatment initiation.


Q: Why do people sometimes stop taking Onisor?

Reasons for discontinuation are often tied to restrictions (contraindications) and documented side effects listed in the official product information. Official product information lists populations for whom the use of Onisor is restricted, as well as adverse events.


Q: Does Onisor cause weight changes?

Official adverse event profiles for Onisor do not explicitly list changes in body weight (gain or loss) as a common side effect. However, decreased appetite is documented as a common event.


Q: Are there specific foods or drinks to avoid while using Onisor?

Official regulatory labels detail instructions for taking the medicine relative to food, which varies by species and condition. However, there are no specific foods or drinks that official documents state must be entirely avoided while using Onisor.


Q: Is Onisor considered a controlled substance?

According to the official product information and national drug classifications, Onisor (robenacoxib) is classified as a Prescription-Only Veterinary Drug (Rx). The drug is not listed as a controlled substance by regulatory bodies.


Q: Does Onisor interact with vitamins or supplements?

Official documents advise caution regarding concurrent use with highly protein-bound active substances. Using them together with Onisor may lead to toxic effects due to competition for protein binding, as described in regulatory warnings.


Q: Is Onisor used for things other than its main purpose? (clarification)

The investigation into whether the drug has an effect on treating related conditions is documented in research summaries. Research investigation is in its early stages, and definitive conclusions about additional uses beyond the approved purpose cannot be drawn at this time.


Q: What age group is Onisor typically used for?

The official label specifies the medication is approved for patients that meet the minimum criteria of four months of age and a body weight of 2.5 kg (or 5.5 lbs) for the oral tablet form. Official documentation does not typically specify a maximum age or a general 'typical' age group.


Q: Does Onisor cause any long-term effects on the heart?

The regulatory safety profile highlights that pre-existing impaired cardiac function is a restriction for use. Furthermore, co-administration with other medicines that prolong the QT interval (a measure of heart rhythm) is not recommended due to an unknown risk of ventricular arrhythmia.


Q: What were the key findings of the major clinical trials for Onisor?

Key findings summarized in regulatory documents include a reported change in symptom severity within seven days of treatment. Additionally, a 52-week extension study observed the continuation of initial responses in a subset of participants.


Q: Do side effects from Onisor usually go away over time?

Official adverse event profiles classify common side effects, such as mild diarrhea or lethargy, as transient effects. This indicates that these effects do not typically last long.


Q: What is the chemical name for Onisor?

The chemical name for Onisor is its active ingredient, robenacoxib. This name is used consistently across all official documentation.


Q: Why is Onisor sometimes prescribed instead of other treatments?

Regulatory documents describe Onisor's unique properties, noting it is a highly selective COX-2 inhibitor (a type of NSAID). It is recognized for its ability to concentrate selectively at the site of inflammation, allowing for targeted action before it is quickly cleared from the general bloodstream.


Q: Does Onisor require a special prescription or monitoring program?

Onisor is classified as a Prescription-Only Veterinary Drug (Rx), requiring professional oversight. Furthermore, official documents state that clinical monitoring may be required if the drug is used concurrently with certain interacting substances.


Q: Is Onisor only used for the condition it was originally approved for?

Official summaries indicate that investigation into the drug's effect on related conditions is currently underway. However, evidence remains limited regarding definitive conclusions about additional approved uses.


Q: What is the minimum age and weight to use Onisor?

According to the official label, the medication is approved for patients that meet the minimum criteria of four months of age. They must also meet a minimum body weight threshold of 2.5 kg (or 5.5 lbs) for the oral tablet formulation.


Q: Is Onisor taken with or without food? (non-directive use condition)

The official instructions regarding administration relative to food vary based on the patient species and clinical condition. For example, chronic oral use in dogs requires the tablet be given without food, while for cats, it may be given either with or without food.


Q: Is it common to feel tired when taking Onisor?

Official adverse event profiles list lethargy as a common event in patients. Lethargy is a description used in medical texts that relates to a state of drowsiness, tiredness, or lack of energy.


Q: Can older adults use Onisor?

Official safety documents note that the use of the drug is possible in older populations. However, the regulatory safety profile specifically notes that elevated renal parameters (measures of kidney function) are reported more frequently in older cats.


Q: Does Onisor affect sleep?

The adverse event profile lists lethargy as a common event, which is related to a state of wakefulness. However, there is no specific mention in official documents of common sleep disturbances such as insomnia or somnolence.


Q: Can I use Onisor if I have kidney issues? (descriptive eligibility)

The official label indicates that using Onisor in patients with pre-existing impaired renal (kidney) function involves additional risks. The label also advises caution with use in patients who are dehydrated or hypovolaemic.


Q: Does Onisor affect hormone levels?

Safety information states that the medicine is strictly contraindicated (must not be used) in pregnant, lactating, or breeding animals. This restriction is based on the fact that safety has not been established in these populations.


Q: How is Onisor different from [similar drug name]? (high-level)

Official documents classify Onisor as a highly selective COX-2 inhibitor (a type of NSAID). The drug's active ingredient, robenacoxib, is described as a synthetic analogue of diclofenac, which provides a basis for high-level comparison to similar drug classes.


Q: Does Onisor interact with common pain relievers?

Yes, official documentation includes a formal restriction. The co-administration of Onisor is strictly contraindicated (must not be given) with other Non-Steroidal Anti-Inflammatory Drugs (NSAIDs), a category that includes many common pain relievers.

How should Onisor be stored and disposed of?

Storage and Disposal Requirements

Official regulatory guidelines establish distinct storage and disposal rules for the two formulations of Onisor (robenacoxib) to ensure product stability and safety.

Formulation Mandatory Storage Conditions Stability Note
Flavored Tablet Store at controlled room temperature (15 C to 25 C) and protect from moisture [FDA, EMA]. Do not use after the expiry date.
Injectable Solution Store in a refrigerator (2 C to 8 C) in the outer carton [EMA]. Use within 28 days after first puncturing the vial.

All formulations must be kept out of the sight and reach of children and pets to prevent accidental exposure, as documented on the official labels. Regarding disposal, unused medicine must not be disposed of via wastewater and must instead be discarded in accordance with local requirements for pharmaceutical waste.

Attention! Always consult to a doctor or pharmacist before using pills or medicines.

Available in countries:

Equivalent of Onisor found in:

A-Z Index: