Injectable Supplements for Horses

Listed below are the most common (non-steroidal) injectable supplements administered to horses to treat for active arthritis and hopefully slow down the development of arthritis. These medications vary in cost, method of administration, and approved use. One of the best known and most commonly used is Adequan. The active ingredient in Adequan is polysulfated glucosaminoglycan (PSGAG) and is FDA approved for intra-muscular and intra-articular use in horses. It is reported that PSGAG-containing products, such as Adequan, work by reducing inflammatory mediators within the joint and help maintain healthy cartilage. Adequan may be given in a loading dose initially for 5-7 treatments and then once monthly or may be administered every 6 months as a loading dose of 7 treatments that are 4-7 days apart.

Figure 1: Molecular structure of Adequan

Figure 2: Intra-articular Adequan

Similar to Adequan , a relatively new supplement in the US is known as Pentosan. The active ingredient in Pentosan is Pentosan Polysulfate Sodium (PPS) and is distinct in molecular structure from Adequan (Figure 1 versus Figure 3) . In humans, PPS is used to treat bladder pain associated with cystitis. In addition, clinical research in humans suggests that PPS may reduce clinical signs associated with arthritis. In horses, clinical and empirical data indicates that regular administration of PPS-containing products reduces clinical signs associated with osteoarthritis. Pentosan is available in the United States as a generic product that is sold through compounding labs (Figure 4). In my practice, it is commonly administered as an intramuscular injection, initially as a loading dose (5 injections, 1 week apart) and then 1-2x per month.

Figure 3: Molecular structure of PPS

Figure 4: Generic Pentosan

A PPS containing product that is licensed for use in horses in the US and FDA approved is PentAssuie (Figure 5) . This product  contains both Pentosan AND N-acetyl glucosamine (PSGAG). N-acetyl glucosamine is a PSGAG but is slightly different in structure compared to Adequan. PentAussie is approved for post surgical lavage and is considered "off label" when administered intra-muscularly. 

Figure 5

The product known as Legend is an injectable supplement approved for use in horses that contains Hyaluronate sodium which is non-sulfated glycosaminoglycan. Hyaluronate is a normal constituent of joint fluid and plays a key role in regulating inflammation within the joint. The product Legend is typically administered intravenously however products containing hyaluronic acid are injected directly into the joint. The frequency of IV administration varies from prior to competition to monthly.  

Figure 6

 Polyglycan (Figure 7) is an injectable supplement that contains a mixture of several productions (Figure 8). It is approved for use in horses but NOT for intravenous administration, which is the most common route of treatment! The product contains hyaluronate, acetyl glucosamine, and chondroitin sulfate (active ingredient in Cosequin).  In my practice, this supplement is administered several days before competition and/or on a monthly basis.

Figure 7

Figure 8

Obviously there is much more information to consider when choosing one of the above for your horse. These are the general guidelines I strongly recommend:

1: Once a horse is old enough to begin training, I recommend an "injectable" supplement to be administered monthly for the duration of that horse's career. Injectable supplements are likely to be superior to oral supplements.
2: Generally speaking intra-muscular injections are less expensive and can be done at the barn by the owner/barn manager. As such, I recommend starting with one of these supplements which include Adequan, Pentosan, and PentAussie.
3: Polyglycan is a great product and should be considered as an "in-addition-to" supplement to be used in horses that are in heavy competition or suffering from advanced osteo-arthritis.
4: The money you spend on a monthly basis for these "injectable" supplements is likely to be the best long term investment you can make for your horse besides having a good farrier and competent veterinarian!!