Initial Treatment of Canine Osteoarthritis in Practice: Myth Versus Reality

Osteoarthritis is a common disease in dogs and cats and is secondary to normal forces on abnormal joints (eg, dysplasia, developmental disorders) or abnormal forces on normal joints caused by instability or trauma.¹ 

Multimodal analgesia is widely accepted as the highest standard of care for managing osteoarthritis pain in veterinary patients because it treats multiple aspects of the pain pathophysiology, including cartilage degradation, the production of inflammatory mediators, the conscious feeling of pain or anxiety, central sensitization, and motor control and strength. Therapeutic strategies are largely based on conventional wisdom because of individual variability with drug class dosing, breed and disease, and availability of adjunctive modalities (eg, physical rehabilitation, acupuncture). 

The following explores common myths encountered in general practice regarding basic management of canine osteoarthritis.

NSAID medications should never be prescribed in a healthy patient unless the owner is willing to pay for baseline bloodwork.

NSAIDs (eg, meloxicam, carprofen) are the most effective and predictable nonopiate, FDA-approved^2,3 prescription medications for treatment of pain from osteoarthritis or surgical trauma in the United States. Therefore, they should always be a primary consideration for the management of any disease with inflammatory pain in healthy patients,³ regardless of baseline blood work. NSAIDs are generally predictable and widely documented in veterinary pain medicine.

Patients with pre-existing disease that could develop chronic dehydration or liver and kidney dysfunction, patients with pre-existing GI disease, and patients with a history of GI sensitivity must be treated differently from a healthy patient. It is important to choose an NSAID with the following key points:

• No studies have shown differences in toxicity or side effects between FDA-approved NSAIDs in dogs.^2-4 However, not all NSAIDs are created equally. The exclusivity of inhibition of cyclooxygenase-2 (the “inflammatory” COX) vary among drugs; this tends to dictate the safety of the drug in different patients. 
• Side effects caused by NSAIDs are rare and should be divided by 3 targeted systems: the GI tract, the liver, and the kidneys. 
• GI side effects are directly caused by the pH or caustic nature of the drug or by drug accumulation in the stomach or intestinal lining.^1,2,4 They are indirectly caused by inhibition of prostaglandin synthesis, a by-product of COX inhibition. Decreased blood flow to the kidneys can be exacerbated by inhibition of prostaglandin synthesis, which can cause acute renal injury. 
• For patients with pre-existing renal disease or decreased renal blood flow due to hypovolemia or shock, NSAID use is not recommended except in the absence of other drug or modality choices. In such cases, careful warnings should be given to pet owners. 
• Hepatic reactions are either dose dependent (eg, accidental overdose) or idiosyncratic (ie, due to an unpredictable adverse response). Due to decreased drug clearance, caution with NSAIDs is advised in patients with liver dysfunction. Of note, idiosyncratic reactions are known to occur within the first 21 days; it is advisable to obtain and evaluate blood work in healthy or diseased patients that are to be maintained on long-term usage. An idiosyncratic reaction to an NSAID is rare, but such a reaction to one NSAID should be interpreted as a reaction to all NSAIDs until further research is conducted.
• NSAID dose reduction has been shown to be only marginally successful for controlling pain in individual patients with osteoarthritis.⁴ Unfortunately, it is common for doctors to prescribe lower doses of NSAIDS in high-risk patients without considering all multimodal options. Caution should be used when relying on minimized dosing of NSAIDs in truly painful patients that deserve better pain control.  

Fat, happy pets live longer.

Obesity is a common comorbidity in dogs with osteoarthritis and imparts mechanical stress on all joints; this exacerbates pain and inflammation as well as impact cellular signaling and interactions with the immune system.^1,6 Inflammatory mediators released from adipose tissue may also directly impact the severity of intra-articular inflammation in joints.⁶ It is well established in the literature that weight-reduction benefits dogs with osteoarthritis by decreasing pain and the degree of osteoarthritis present. There are additional benefits to weight loss, such as improved cardiovascular health.^6-9

Implementation of a weight-loss program for dogs can include regular weigh-ins at the clinic, physical rehabilitation, calorie counting, and/or prescription weight-loss diets. Pet obesity is a lifestyle choice by the owner; therefore, many physical and psychological factors of the pet’s family must be considered to ensure that a weight loss plan is effective. Fat pets do not live longer, and they suffer from more pain caused by osteoarthritis.

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