Injectable Disease-Modifying Osteoarthritis Drugs (DMOADs) in Cats

What is osteoarthritis?

Osteoarthritis (OA) is a progressive, degenerative disease of the joints. It is one of the most common chronic diseases in cats, although it is dramatically under-recognized. It is estimated that more than 90% of cats over 10 years of age have radiographic (X-ray) evidence of OA.

What causes osteoarthritis?

OA can be caused by a variety of things.

• A cat’s conformation (how their body is put together) can cause them extra stress and strain on their joints.
• Some developmental abnormalities with genetic and nutritional influences such as hip dysplasia can prevent joints from forming normally. Joints affected by dysplasia tend to develop OA early in life.
• Some genetic mutations can lead to abnormal cartilage that results in early OA (e.g., Scottish Fold).
• OA can also result from a traumatic injury to a joint (e.g., falling from a tree or being hit by a car).

Cats 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 cat with OA?

Your veterinarian is the best source for a comprehensive OA management plan. If your cat is overweight or obese, that is the best place to start, but there is much more that can be done to help support the joints of a cat with OA. In addition to diet modifications, exercise, weight loss, nonsteroidal anti-inflammatory drugs (NSAIDs), and anti-nerve growth factor antibody treatment (Solensia®), management strategies for OA may include a disease-modifying osteoarthritis drug (DMOAD).

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 (off-label) in cats 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.

Are DMOADs safe for cats?

PSGAG and PPS are both off label for use in cats, but they are both considered safe. Many drugs are commonly prescribed for off-label use in veterinary medicine. It’s important to follow your veterinarian’s recommendation for their use and to report any concerns to your veterinarian.

How are DMOADs given?

Both PSGAG and PPS can be given as subcutaneous injections (under the skin), and can often be given at home after instruction by your veterinary team. Your veterinarian will carefully weigh the advantages and disadvantages of ongoing treatment and will discuss the treatment strategy with you. Typically, DMOADs are given as a series of injections that may be followed with ongoing injections at certain intervals.

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 cats with bleeding disorders.

How long 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 cat by the end of the series.

How long will my cat 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 is generally well-tolerated. OA is never cured; it is only managed. For this reason, additional joint support therapies are recommended in cats with OA.

Cats with OA present a unique challenge to veterinarians because of the small number of medications available for them. In many cases, ongoing DMOAD dosing can reduce a cat’s need for pain medications that have a higher risk of side effects (e.g., NSAIDs) or even allow for a temporary withdrawal of these medications.