Injectable Disease-Modifying Osteoarthritis Drugs (DMOADs) in Dogs

What is osteoarthritis?

Osteoarthritis (OA) is a progressive, degenerative disease of the joints. It is one of the most common chronic diseases of dogs. By some estimates, 20% of dogs of all ages are affected by OA.

What causes osteoarthritis?

OA can be caused by a variety of things.

• A dog's conformation (how their body is put together) can cause them to move in ways that put extra stress and strain on the joints. 
• Some developmental abnormalities with genetic and nutritional influences, such as hip dysplasia and elbow dysplasia, can prevent joints from forming normally. Joints affected by dysplasia tend to develop OA early in life. 
• OA can result from a traumatic injury to a joint (e.g., being hit by a car).

Dogs that are overweight or obese have an increased risk of OA. The inflammatory chemicals produced by fat cells, combined with the repeated stress that excess weight places on the joints over time, contribute to the development and progression of OA and its degenerative, painful effects.

What can I do to help my dog with OA?

Your veterinarian is the best source for a comprehensive OA management plan. If your dog is overweight or obese, that is the best place to start, but much more can be done to help support the joints of a dog with OA. Management strategies for OA may include diet modifications, exercise, weight loss, nonsteroidal anti-inflammatory drugs (NSAIDs), and disease-modifying osteoarthritis drugs (DMOADs).

What is a DMOAD?

A disease-modifying osteoarthritis drug (DMOAD) is a medication that slows or changes how OA progresses. There are two common DMOADs used in dogs with OA, and both are given by injection.

Polysulfated glycosaminoglycan or PSGAG (Adequan®):

• Reduces joint inflammation and decreases pain.
• Prevents the release of damaging inflammatory chemicals in the joint.
• Increases production of components of healthy cartilage (collagen, glycosaminoglycan).
• Improves joint lubrication, which improves joint mobility and increases comfort.

Pentosan polysulfate sodium or PPS (Cartrophen®):

• Stimulates cartilage production.
• Increases blood supply and nutrition to the joint.
• Reduces inflammation (anti-inflammatory).
• Inhibits the release of damaging inflammatory chemicals in the joint.
• Improves joint lubrication, which improves joint mobility and increases comfort.
• Is approved by Health Canada but not approved by the U.S. Food and Drug Administration (FDA).

A third option administered differently is Synovetin OA®.  Synovetin OA® is considered a disease-modifying osteoarthritic device that is injected directly into affected joints. It kills harmful inflammatory cells in the joint for a sustained time, reducing joint damage, inflammation, and pain.

How often are DMOAD injections given?

Each injectable DMOAD has its own recommended route and frequency.

• PSGAG is generally given in the muscle or in the skin as a series of 8 injections over 4 weeks. 
• PPS is given in the skin once weekly over 4 weeks.
• Synovetin OA® is given directly into the joint once a year.

Do DMOADs have any side effects?

PSGAG and PPS may cause mild side effects.

• Mild, short-lived diarrhea has been reported.
• Vomiting, lethargy, and loss of appetite have been reported but are not common.
• PSGAG and PPS are not recommended for use in dogs with bleeding disorders. 

How soon after starting a DMOAD will I notice improvements?

Both PSGAG and PPS are given as a series of injections, so you should notice an improvement in your dog by the end of the series. With Synovetin OA® injection, you should see improvements within 2 to 4 weeks, but it may take up to 2 months, depending on the severity of the arthritis.

How long will my dog need DMOAD injections?

OA is a progressive, life-long disease. Fortunately, DMOADs are generally considered beneficial over the long term. The risk of adverse side effects is relatively low, so long-term use of DMOADs are generally well-tolerated. OA is never cured; it is only managed. For this reason, additional joint support therapies are recommended in dogs with OA.

DMOADs are often recommended as multimodal therapy for OA that can reduce a dog’s need for pain medications that have a higher risk of side effects (e.g., NSAIDs).