Horse Side Vet Guide ®

Equine Health Resource

Pentosan Polysulfate Sodium, PPS



Pentosan polysulfate (PPS) is a substance created from xylan, a structural carbohydrate extract of certain plants. Recent research suggests that PPS may have value in the treatment of osteoarthritis in the horse.

PPS has been shown to increase the health of cartilage by increasing proteoglycan content within it. PPS is also said to increase hyaluronic acid synthesis within the joint, causing increased viscosity of joint and tendon sheath fluid. PPS has actions that improve blood flow to the joint. It also has an anti-inflammatory action.

PPS is not approved by the FDA as an injection, at the current time, and has mostly been used in Australia and Europe. It is available in the U.S. through compounding pharmacies at the time of this writing. A new product is now commercially available in the US but it is still not FDA approved for injectable use in the horse.

A commercial preparation contains a lower dose of pentosan with HA and glucosamine. Effectiveness of this product is questionable based on a 2014 paper.

PPS is known as a “disease-modifying drug” meaning that it changes the health of the joint in positive ways, and in so doing slows the progression of arthritis. It has no direct pain-relieving (analgesic) effects.

Recent research suggests that there are positive effects of PPS on joint health but that the lameness modifying effects may be subtle. That same study suggests that the current recommended dose may be low, and possibly that doubling of the dose might improve effectiveness. There is a mild increase in side effects with the increased dose.

PPS is an intramuscular injection given to horses as a joint therapy. Other formulations of the drug may be given orally or intravenously. PPS is typically given as a loading dose, once weekly for 5-8 weeks, and then once monthly thereafter. The dose that was used in the study was 3mg/kg IM, but your vet will determine dosing.

Although this drug is currently available without a prescription, talk to your vet about whether PPS is the best choice for your horse. Your vet will consider your horse’s overall health history, the horse’s use, the diagnosis, and any contraindications. You and your vet can also develop a plan to evaluate the efficacy of this treatment. Although pentosan  is currently a legal medication in FEI competition, it is wise to check FEI or competition prohibited substance rules frequently to be sure this is still the case.

This Treatment Might be used for a horse exhibiting these signsRelated Observations

Consider Potential Side Effects & Complications

The primary side effect is mildly reduced clotting function.

Like any drug, occasionally a horse may have an allergic reaction to PPS.

Consider Reasons Not To Use This Treatment

PPS should not be used in horses that have recently undergone surgery, those with known clotting or bleeding problems, or those with autoimmune disease.

PPS is not approved by the FDA at the current time, and has mostly been used in Australia and Europe. It is available through compounding pharmacies at the time of this writing. A new product is now commercially available in the US but it is still not FDA approved for injectable use in the horse.

PPS is best not used within 48 hours of strenuous exercise. This is because of the potential for trauma with exercise, and the potential for bleeding.

Is It working? Timeframe for effect

In most cases, horse owners report an improvement in lameness after 3-5 doses. Research suggests that the changes may be subtle. An objective evaluation of the horse before treatment and during treatment helps determine the effectiveness of the treatment.

Questions To Ask My Vet

  • How does PPS compare to Adequan and oral joint supplements?
  • What is the difference between PPS and Adequan?
  • Why do you recommend PPS over these other products?
  • What has been your personal experience with this medication?
  • What concerns should I have given that this drug is compounded?
  • How can I tell whether this treatment is working?
Author: Doug Thal DVM Dipl. ABVP

RELATED REFERENCES website. Marcella, KR. Research points to pentosan polysulfate to treat equine osteoarthritis. June 2012. Available at: Accessed 2014.McIlwraith CW, Frisbie DD, Kawcak CE. Evaluation of intramuscularly administered sodium pentosan polysulfate for treatment of experimentally induced osteoarthritis in horses. Am J Vet Res 2012;73(5):628-33.Koenig TJ1, Dart AJ, McIlwraith CW, et al. Treatment of experimentally induced osteoarthritis in horses using an intravenous combination of sodium pentosan polysulfate, N-acetyl glucosamine, and sodium hyaluronan. Vet Surg. 2014: 43(5):612-22.


We're not around right now. But you can send us an email and we'll get back to you, asap.