Bisphosphonates can help equine practitioners in treating the clinical signs of navicular syndrome in horses 4 years and older, if used properly.
Chronic pain associated with navicular syndrome is a common problem that equine practitioners see. It has been reported as causing one-third of all chronic forelimb lameness in horses. It is considered chronic because of the pain arising from the navicular bone and closely related structures such as the collateral suspensory ligaments, distal sesamoidean impar ligament, navicular bursa and the deep digital flexor tendon.1
“Treatment is not always clear because both soft and hard structures can affect navicular syndrome and these are treated very differently,” says Shelly Derks, Marketing Manager – Equine and Specialty Products.
Treatment options used to be limited. However, in 2014, the U.S. Food and Drug Administration (FDA) approved Osphos® (clodronate injection) and Tildren® (tiludronate disodium) to treat the clinical signs associated with navicular syndrome. They currently remain the only FDA approved bisphosphonates for veterinary medicine.
Osphos, a bisphosphonate, is a relatively new class of drug to the equine market, although it has been used for decades in humans, Derks says. It has gained wide acceptance in equine veterinary medicine to address navicular syndrome in horses in an effective and non-invasive manner.
Normally, the amount of bone formed during bone remodeling equals the amount destroyed, but this is not the case in diseased bone. Bisphosphonates like Osphos regulate bone metabolism through inhibition of bone resorption and bring the balance of osteoclast (cells that break down bone) and osteoblasts (cells that build bone) back to normal by reducing the activity of the osteoclasts.2
However, with the new solutions, come questions regarding the proper use of the drug. Dechra Veterinary Products hosted a panel discussion, “A Review of Osphos® (clodronate injection) in a clinic setting” at the AAEP Convention. “There has been many off-label uses of this drug for other bone diseases and I think attendees wanted to hear what their peers had to say,” Derks says.
There have been newer, non-approved and much more potent bisphosphonates appearing, and veterinarians wanted to know the benefits and risks of those, Derks says. “Questions about using it for other off-label uses were asked. One discussion was led around using this as preventative vs. treatment, which is absolutely against our label claim and not recommended.”
Indeed, clinical data and investigations strongly support adhering to the Osphos package insert (label), according to Dechra. “It is imperative every veterinarian consider the therapeutic use of Osphos on a patient-by-patient basis to assure the best clinical outcomes,” the company said in a release leading up to its panel discussion at AAEP.
1 Adam’s and Stashak’s lameness in horses-6th ed./ [edited by] Gary M. Baxter. Wiley-Blackwell, West Sussex, UK 2011; pp 475-593.
2 Fleisch, H. Biological effects. Bisphosphonates in bone disease: from the laboratory to the patient. [2.3.2], 34-51. 2000. San Diego, Academic Press.
The following are questions sales reps can ask their veterinary customers about navicular syndrome and treatment:
- • “How many cases of navicular syndrome are you diagnosing and are you referring those to specialty clinics or treating them yourself?”
- • “Are you aware there is a treatment that involves an intramuscular injection that can be given every 3-6 months to control the clinical signs of navicular syndrome in the horse?”
- • “Are you aware of the income this can bring your practice by ensuring you see the horse every 6 months to re-evaluate?”
Because each horse has unique performance characteristics, evaluating lameness can be challenging. Experienced riders may detect minor alterations in gait before they are apparent to an observer. Lameness may appear as a subtle shortening of the stride, or the condition may be so severe that the horse will not bear weight on the affected limb.
A lameness grading system has been developed by the AAEP to aid both communication and record-keeping. The scale ranges from zero to five, with zero being no perceptible lameness, and five being most extreme. The AAEP guidelines explain the grading system this way:
- •0 – Lameness not perceptible under any circumstances.
- •1 – Lameness is difficult to observe and is not consistently apparent, regardless of circumstances (e.g. under saddle, circling, inclines, hard surface, etc.).
- •2– Lameness is difficult to observe at a walk or when trotting in a straight line but consistently apparent under certain circumstances (e.g. weight-carrying, circling, inclines, hard surface, etc.).
- •3 – Lameness is consistently observable at a trot under all circumstances.
- •4 – Lameness is obvious at a walk.
- •5 – Lameness produces minimal weight bearing in motion and/or at rest or a complete inability to move.
Source: AAEP website, https://aaep.org/horsehealth/lameness-exams-evaluating-lame-horse