Navicular disease is a common cause of chronic forelimb lameness in working and athletic horses.1 It involves inflammation or degeneration of the navicular bone and adjacent tissues. It is not to be confused with laminitis; although some of the treatment regimens are the same, laminitis is a condition of the hooves themselves and primarily involves the digital laminae within the hoof.2 

The cause of navicular disease (or navicular syndrome) is not precisely known, although the available literature suggests that damage to the navicular bone may occur due to interference with blood supply or trauma to the bone.1,3 The navicular bone is a small flattened bone lying posterior to the coffin joint. Through a series of ligaments and tendons, it performs as a pulley of sorts within the hoof.

Navicular disease is generally described as being slow or intermittent in onset, ultimately presenting with bilateral lameness,1 after which the condition progressively deteriorates. Navicular disease appears to have a hereditary component, and usually occurs in horses from 8 years old on. It tends to be overrepresented in some breeds and rarer in others.

Navicular Disease in the Horse

Until two decades ago, it was believed that navicular disease was solely a degeneration of the navicular bone, but it is now widely accepted that this is just part of the condition. Navicular bone disease forms part of navicular syndrome, with the other part being the involvement and degeneration or damage to other structures in the foot. The foot structures that can be potentially involved in navicular syndrome include:

• Navicular bone

• Navicular bursa

• Suspensory ligaments of the navicular bone

• Impar ligament  

• Deep digital flexor tendon 

• Coffin joint  

• Collateral ligaments of the coffin joint

In a horse presenting with navicular disease, any combination of these structures may be involved.

Isoxsuprine for Horses

After parenteral administration, horses may show signs of CNS stimulation (uneasiness, hyperexcitability, nose-rubbing), tachycardia, and increased cardiac output, or sweating. Signs are typically short-lived. Adverse effects are unlikely after oral administration but hypotension, tachycardia, and GI effects are possible.1

Where to buy Isoxsuprine 

Isoxsuprine is available in the U.S. through several pharmaceutical manufacturers and through veterinary custom compounding companies. Please consult your veterinarian prior to beginning any treatment regimen.

FOR RX ONLY: A valid prescription from a licensed veterinarian is required for dispensing this medication.

1Merck Veterinary Manual.

2vcahospitals.com.

3thehorse.com.