Heaves is a common, allergic respiratory disease of horses characterized by chronic cough, nasal discharge and respiratory difficulty. It is also known as Recurrent Airway Obstruction (RAO), Chronic Obstructive Pulmonary Disease (COPD) broken wind and emphysema. Heaves in horses is most analogous to asthma in humans. Episodes are usually observed when a horse is stabled, bedded on straw and fed hay.¹ In most cases, eliminating these factors can result in a reduction of clinical signs.

Most horses that suffer from heaves will begin exhibiting symptoms by the age of nine years. Approximately 12% of horses will exhibit some measure of allergen-related lower airway disease, and over 50% of horses that present for evaluation of respiratory disease will be diagnosed with heaves.² RAO occurs more often in the winter when horses are stabled more frequently and differs from summer pasture–related obstructive pulmonary disease, which is found in southern regions where horses are kept on pasture throughout the year.

While heaves does appear to have a heritable component, there is no correlation between breed or gender. In most cases, individual horses will have a broad range of sensitivity to allergens (usually molds) and severity of clinical signs.

Clinical Signs of Heaves in Horses

Horses with heaves will exhibit flared nostrils and difficulty breathing. The abdominal muscles are recruited to assist with expiration, resulting in the classic heave line produced by hypertrophy of these muscles.² Mild and moderately affected horses often present with minimal clinical signs at rest, with coughing and exercise intolerance occurring during performance. 

Diagnoses of heaves are determined on the basis of history and characteristic physical examination findings. Radiographs of the chest and sampling of respiratory secretions is indicated to provide additional information in some cases.²

Isoflupredone Acetate for Equines

Corticosteroids are currently the most effective drugs for the control of heaves. They are also widely used for the treatment of horses suffering from painful joint conditions.

Isoflupredone (isoflupredone acetate) is an injectable glucocorticoid that is labeled for use in cattle (dairy cows), horses, and swine for anti-inflammatory and immunosuppressive effects. Labeled indications include: adjunctive treatment of bovine ketosis, alleviating pain and lameness associated with musculoskeletal conditions, acute hypersensitivity reactions, adjunctive treatment of overwhelming infections with severe toxicity, shock, supportive therapy in the treatment of stress conditions, dystocia, retained placenta, inflammatory ocular conditions, snakebite, and parturient paresis.³

Isoflupredone’s anti-inflammatory potency is approximately 17 times that of hydrocortisone. Its glucocorticoid activity was 50 times that of hydrocortisone and 10 times that of prednisolone as measured by liver glycogen deposition in rats.³Isoflupredone reportedly has some mineralocorticoid effects, and can cause hypokalemia.

Adverse effects are generally associated with long-term administration of glucocorticoids, particularly if given at higher dosages; these effects generally are manifested as signs of hyperadrenocorticism.³ Recent research has indicated, however, that even single doses administered to dairy cattle can cause hypokalemia. Isoflupredone is less likely to cause early parturition than dexamethasone or betamethasone, but its use should be avoided during pregnancy.

Dosage recommendations for the use of isoflupredone in horses are as follows (adapted from Plumb’s Veterinary Drugs):

• Labeled systemic indications (FDA-approved): 5 – 20 mg (total dose) IM repeated as necessary. For intrasynovial administration: 5 – 20 mg or more depending on the size of the joint cavity. 
• Intraarticular administration (extra-label): 4 – 20 mg; has a short to medium duration of action.
• Heaves (extra-label): 0.03 mg/kg IM once daily for 14 days.

NOTE: The Association of Racing Commissioners International Uniform Classification Guidelines for Foreign Substances has designated isoflupredone a CLASS 4 DRUG.

Where to buy Isoflupredone Acetate 

Isoflupredone acetate is available in the U.S. through pharmaceutical manufacturers and veterinary custom compounding pharmacies. ISOFLUPREDONE ACETATE 2MG/ML (100ML) by NexGen Pharmaceuticals is indicated for the treatment of heaves, as well as pain and lameness associated with certain joint conditions. 

Isoflupredone acetate carries several potential drug interactions. 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.

¹Picandet, V., et. al. Comparison of efficacy and tolerability of isoflupredone and dexamethasone in the treatment of horses affected with recurrent airway obstruction (‘heaves’). Equine Veterinary Journal, 5 January 2010.

²Merck Veterinary Manual.

³Plumb’s Veterinary Drugs.