Osteoarthritis Treatments Part II: Systemic and Intra – Articular Therapies

Earlier this fall, we discussed how non-steroidal anti-inflammatory drugs and joint supplements can improve comfort.  This month, we will discuss how systemic therapies, such as Adequan, Legend, and Pentosan, and intra-articular medications help arthritic joints, as well as some future therapies.

Systemic Therapies (Adequan, Legend, and Pentosan)

The next step in treating osteoarthritis is often a systemic therapy.  Systemic therapies are administered either intravenously or intramuscularly and have the advantage of treating multiple affected joints.  They often have more affect than oral joint supplements, but are not as good at relieving pain as the NSAIDs or joint injections.  These products do have the advantage of modifying the progression of the disease process and are often used as general maintenance for cartilage health.

Hyaluronan (HA) (Legend), polysulfated glycosaminoglycans (PSGAGs) (Adequan), and pentosan polysulfate (Pentosan) all have different mechanisms of improving cartilage health.  In our experience, HA has more of an effect when administered directly into the joint, as opposed to the intravenous form (Legend).  However, a study did show Legend improved lameness in horses with arthritis.  Adequan has also had studies that prove effectiveness, and in our experience, has been beneficial in treating this disease.  Pentosan is a proven, but newer drug in this country.  Pentosan is available in the US as a compounded product, meaning it is made in small batches for specific patients and without the guarantee of a pharmaceutical company.  Pentosan has helped many of our patients.  Adequan has recently been on manufacturers’ backorder and our stock of this product has been limited.  Adequan is supposed to be back on the market soon.

injecting hock compresssed

Dr. McAndrews injecting one of the hock joints.

Intra-Articular Therapies (Joint Injections)

Intra-articular therapies deliver potent medications directly to the affected joint.  A combination of steroids, antibiotics, local anesthetic, and HA are most frequently administered.  Steroids have a strong anti-inflammatory effect and also have a disease modifying affect, significantly improving lameness in most affected horses.  Much has been studied about the deleterious affects of steroids in joints but at the low doses we use, the activity level of most horses, and the frequency of most injections, this adverse affect is minimal.

In some joints, HA is also administered for its effects in improving cartilage health.  A combination of HA and steroid can prolong the beneficial affect of the joint injection.  Adequan can also be administered intra-articularly to improve cartilage health.  Regenerative therapies, such as PRP and IRAP, are used intra-articularly to manage OA with some success.

Future Therapies

Bisphosphonates (Tildren) inhibit bone resorption and may help in diseases with increased bone turnover, such as OA.  This drug is already being used for the treatment of certain types of navicular syndrome and more studies are pending.

Tetracyclines such as doxycycline and minocycline, are antibiotics that have been found to have anti-inflammatory effects.  These antibiotics have been used to treat OA in humans.  Studies are underway to decrease the antibiotic properties of these drugs but keep the anti-inflammatory effect.

In summary, NSAIDs are often used for brief periods to manage short term pain, oral joint supplements can be of benefit in mild cases of OA, systemic medications help moderate cases and cases with multiple joints effected, and intra-articular medications have the most potent affect in improving lameness.