Mechanism of action
The known properties of PPS have for years provided a reasonable assurance of what was happening on a physiologic basis within
the sport horse, but only recently have researchers begun to investigate and prove that the suspected mechanisms are in fact
Researchers in the Department of Anatomy at the University of Bristol in Langford, England, were the first to demonstrate
that intramuscular injections of PPS showed sufficient concentration of the drug in synovial or joint fluid.4
This proved that injecting PPS into a horse's muscles eventually got the drug into the joints, and "the concentration
was sufficient to elicit a potential therapeutic effect on synovial metabolism, and possibly also to stimulate proteoglycan
synthesis and reduce matrix metalloproteinase (one of the major cartilage degeneration agents) activities in articular or
More recently, researchers at the Orthopaedic Research Center at the College of Veterinary Medicine at Colorado State University
looked at the drug's actions on 18 horses that underwent surgically induced osteoarthritis.5 This study was one of the first to investigate PPS use in a clinical setting, and various parameters were used to evaluate
the drug's efficiency, including blinded lameness and range of motion examinations (research evaluators didn't know which
horses received drug vs. placebo), blood and joint fluid analysis and serial radiographs.
The study's authors concluded that PPS use produced trends that were not highly significant but showed more positive recordable
differences between the treatment and placebo groups histologically rather than clinically. They concluded that PPS does have
a beneficial therapeutic effect but that further study is indicated.5
They also found that PPS may not be sufficiently potent to demonstrate a clinical effect at the current dose of 3 mg/kg, which
may be the reason many practitioners are recommending a higher dose of 6 mg/kg. Caution always should be used and attention
to timing and dosage is important.
PPS is not currently available in the United States, although some laboratories are compounding it for extralabel use. Caution
should be exercised with any such preparation. PPS is generally given intramuscularly once weekly for four to five weeks and
monthly thereafter. Clinical response is usually seen after the first two or three doses. It's too early to tell if PPS is
going to be the next big thing or merely a product whose time has come and gone. Further testing will determine how PPS—the
wonder from down under—fits into what's currently available for arthritis in horses, and whether the second time around is
Dr. Marcella is an equine practitioner in Canton, Ga.
1. Biopharm Australia Pty Ltd. Cartrophen Equine Forte: a disease modifying osteoarthritis drug. Available at:
2. Dart A, Perkins N, Dowling, et al. The effect of three different doses of sodium pentosan polysulphate on haematological and
haemostatic variables in adult horses. Aust Vet J 2001;79(9):624-627.
3. Maffrand JP, Herbert JM, Bernat A, et al. Experimental and clinical pharmacology of pentosan polysulfate. Semin Thromb Hemost 1991;17(Suppl. 2):186-198.
4. Fuller CJ, Ghosh P, Barr AR. Plasma and synovial fluid concentrations of calcium pentosan polysulphate achieved in the horse
following intramuscular injection. Equine Vet J 2002;34(1):61-64.
5. 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):628-633.