AVMA News

FDA approves first injectable pentosan for osteoarthritis in horses

December 26, 2022

The Food and Drug Administration announced Dec. 20 that the agency has approved Zycosan, which contains pentosan polysulfate sodium for injection, to control clinical signs associated with osteoarthritis in horses. Zycosan is a heparinlike compound and is the first injectable pentosan product to receive FDA approval.

According to the FDA, Zycosan will be an important addition to the available approved drugs to control the clinical signs of osteoarthritis in horses. Unapproved injectable formulations of pentosan, including compounded formulations, have a long history of use in horses, but Zycosan is the first injectable pentosan product to have met FDA standards for safety, efficacy, and consistent manufacturing processes. The agency strongly encourages veterinarians to use legally marketed, FDA-approved Zycosan when pentosan is indicated for use in an equine patient.

A veterinarian performs an ultrasound examination of a horse’s lame leg.

Anzac Animal Health LLC, the sponsor of Zycosan, conducted a field study in client-owned horses that had lameness in one leg and were diagnosed with osteoarthritis in the lame leg. On day 28, more horses in the Zycosan-treated group had improved lameness grades, compared with a control group.

Because pentosan polysulfate sodium is a weak anticoagulant, people who take an anticoagulant should use caution when handling or administering Zycosan, according to the FDA.

Zycosan should be administered at a dose of 3 mg/kg (1.4 mg/lb) by intramuscular injection once weekly for four weeks. The product is supplied in a 7.5-mL single-use vial.

For more information, see the FDA’s letter to veterinarians, letter to pharmacists, and summary of the approval for Zycosan (PDF).