Managing Osteoarthritis in Dogs: A Comprehensive Guide

Addressing pain pharmacologically is a cornerstone of OA management. The following drug classes are commonly used in veterinary practice, with varying levels of evidence and application:

• Non-Steroidal Anti-Inflammatory Drugs (NSAIDs)

Examples: Carprofen, Meloxicam, Firocoxib, Robenacoxib, Enflicoxib, Mavacoxib
Mechanism: Inhibit cyclooxygenase enzymes (primarily COX-2), reducing production of pro-inflammatory prostaglandins.
Efficacy: Considered first-line for OA, NSAIDs consistently reduce pain and inflammation, and improve mobility (Reymond et al. 2012; Payne-Johnson et al. 2015, Pye et al 2024).
Considerations: Potential for gastrointestinal, hepatic, or renal adverse effect, necessitating regular monitoring.

• Piprants

Example: Grapiprant (Galliprant®)
Mechanism: Selectively blocks the EP4 receptor, a key mediator of pain and inflammation, without inhibiting COX enzymes.
Efficacy: Demonstrated modest improvements in pain and function in large placebo-controlled trials, though less effective than NSAIDs in direct comparisons.
Considerations: Gastrointestinal safety is favourable. May be preferred in NSAID-sensitive dogs or early OA cases.

• Paracetamol (Acetaminophen)

Mechanism: Likely involves central COX-3 inhibition and modulation of serotonergic and endocannabinoid pathways.
Efficacy: Mild analgesia with no anti-inflammatory effect. Limited evidence supports adjunctive use.
Considerations: Must be used cautiously due to risk of hepatotoxicity. Contraindicated in cats. Could be of use in patients where NSAID use is contraindicated.

• Opioids

Examples: Codeine, Methadone, Morphine, Tramadol
Mechanism: μ-opioid receptor agonists; tramadol also inhibits serotonin and norepinephrine reuptake.
Efficacy: Injectable opioids are effective for acute pain but not suitable for long-term OA use. Tramadol shows poor bioavailability and inconsistent benefit in dogs.
Considerations: Risk of sedation, regulatory limitations, and limited evidence of efficacy in chronic pain. Codeine is poorly absorbed orally in dogs.

• Gabapentinoids

Examples: Gabapentin, Pregabalin
Mechanism: Modulate voltage-gated calcium channels, reducing neurotransmitter release involved in pain transmission.
Efficacy: Useful in managing chronic and neuropathic pain, particularly as adjuncts. Evidence is anecdotal or based on open-label studies.
Considerations: May cause sedation or ataxia. Efficacy may wane over time.

• NMDA Antagonists

Example: Amantadine
Mechanism: Blocks NMDA receptors, reducing central sensitization and “wind-up” pain.
Efficacy: Shown to improve outcomes when added to NSAID therapy, particularly in dogs with refractory pain.
Considerations: Generally well tolerated. Should be used as an adjunct therapy and cases of chronic pain/dorsal horn wind up.

• Disease-Modifying Osteoarthritis Drugs (DMOADs)

Examples: Cartrophen Vet®, Synovan® (Pentosan Polysulfate Sodium, PPS)
Mechanism: PPS is thought to slow OA progression through anti-inflammatory, fibrinolytic, and chondroprotective effects. It may inhibit cartilage-degrading enzymes, promote proteoglycan synthesis, and improve joint perfusion.
Efficacy: Despite widespread use, clinical evidence for Pentosan Polysulfate remains limited and outdated. A 2024 systematic review by Pye et al. found no new evidence in the past decade supporting its efficacy. Earlier reviews (e.g. Aragon et al. 2007) described weak and inconsistent evidence, insufficient to make strong clinical recommendations. Most published studies are small, lack placebo controls, and use subjective outcome measures.
Considerations: DMOADs are generally safe and well tolerated. It may be considered as a last-line adjunct in multimodal OA management, particularly if NSAIDs are contraindicated. Continued use should be based on demonstrable clinical improvement.

• Monoclonal Antibodies

Example: Bedinvetmab (Librela®, Beransa®)
Mechanism: Monthly injection targeting nerve growth factor (NGF), a central mediator of chronic pain pathways.
Efficacy: RCTs demonstrate improved mobility and reduced pain in dogs with OA.
Safety Concerns: A 2025 study by Farrell et al. reported a significantly increased rate of musculoskeletal adverse events (e.g., tendon rupture, joint instability, and polyarthritis) in dogs receiving bedinvetmab compared to NSAIDs. The pattern is reminiscent of human rapidly progressive OA linked to anti-NGF therapies.
Considerations: Careful case selection and informed consent are advised. Monitoring for adverse events is essential.

• Cannabinoids

Examples: Cannabidiol (CBD) oil, hemp-derived extracts
Mechanism: Cannabinoids such as CBD act on the endocannabinoid system (ECS), particularly CB1 and CB2 receptors. In the context of OA, CB2 receptor activation may help modulate inflammation, immune cell activity, and pain perception.

Efficacy: Early studies in dogs suggest that CBD may reduce pain and increase activity levels in dogs with OA. In a randomised, placebo-controlled crossover trial, Gamble et al. (2018) reported significant owner-reported improvements in pain and mobility in dogs; however, evidence remains limited, and results vary depending on product formulation, dose, and individual variability. A 2020 study by Mejia et al. noted improvement in pain scores when CBD was combined with other analgesics.

Considerations: CBD is generally well tolerated, but long-term safety data are lacking, and there is potential for drug interactions (e.g., with NSAIDs or anti-epileptics). Hepatic enzyme elevations have been reported. Product quality and dosing consistency vary widely across commercial products, as few are regulated. With veterinary supervision, CBD can be considered an adjunctive therapy.

• Platelet-Rich Plasma (PRP)

Example: Autologous (patient-derived) PRP injections (commercial kits and in-practice centrifugation systems)

Mechanism: PRP is a concentrated suspension of platelets derived from the patient’s own blood. When activated, platelets release a variety of growth factors and cytokines that modulate inflammation, tissue repair, and matrix remodelling. In osteoarthritic joints, PRP is theorized to reduce synovitis and promote cartilage homeostasis.

Efficacy: Preliminary studies and case series suggest that intra-articular PRP may reduce pain and improve limb function in dogs with OA, particularly in the short to medium term. However, controlled trials are limited, and there is high variability in PRP preparation methods, platelet concentrations, and injection protocols, making comparisons across studies difficult.

Considerations: PRP is autologous, reducing the risk of immunogenic reaction. Adverse effects are rare, but the lack of standardisation and short-lived effects are notable limitations. Repeated injections may be necessary. Further large-scale, randomised controlled studies are needed to determine optimal protocols and long-term efficacy.

• Mesenchymal Stem Cells (MSCs)

Example: Adipose-derived or bone marrow-derived mesenchymal stem cell injections

Mechanism: MSCs are multipotent stromal cells capable of differentiating into various tissue types, including cartilage, bone, and fat. In the context of OA, MSCs are proposed to reduce synovitis, inhibit cartilage breakdown, and promote tissue repair within the joint.

Efficacy: Several clinical studies and open-label trials report subjective improvement in lameness, pain, and quality of life in dogs treated with intra-articular MSCs. Variability in cell sources, preparation methods, and dosing protocols makes it challenging to draw broad conclusions. Objective outcome measures and long-term follow-up data remain limited.

Considerations: MSC therapy is generally well tolerated, with low risk of adverse reactions, particularly with patient-derived preparations. Cost and accessibility remain barriers for routine use.