Table 12-13.
Drugs used in the treatment of heaves in horses
| Drug | Dose and frequency | Route | Comments | |
|---|---|---|---|---|
| Bronchodilators | ||||
| β2-agonists | Clenbuterol | 0.8–3.2 µg/kg q12 hourly | Oral or IV | Initial therapy with lowest dose. |
| Gradual increments depending on response. For short-term therapy pending environmental control and corticosteroid administration. | ||||
| Albuterol | 50 µg/kg | Oral | Unknown and doubtful efficacy. | |
| Albuterol | 1–3 µg/kg q6–12 hours | Inhalation | Has short duration of action (1 hour). | |
| Can be combined with ipratropium to prolong duration of bronchodilation. | ||||
| Fenoterol | 2–4 µg/kg as needed | Inhalation | Short duration of action. | |
| Pirbuterol | 1–2 µg/kg as needed | Inhalation | Short duration of action. | |
| Salmeterol | 0.5–1.0 µg/kg q6–12 hours | Inhalation | Longest acting β2-agonist available for inhalation. | |
| Terbutaline | 0.2 mg/kg as needed | Inhalation | Marked adverse effects including tachycardia. Not absorbed after oral administration. | |
| Terbutaline | 0.005 mg/kg as needed | IV | Marked adverse effects, including sweating and tachycardia. | |
| Parasympatholytics | Ipratropium | 0.5–3.0 µg/kg q4–6 h | Inhalation | Usually combined with albuterol for rapidity of onset of bronchodilation. Duration of action is ~6 h. |
| Glycopyrrolate | 5 µg/kg as needed | IV or IM | Useful for short-term or emergency relief of bronchoconstriction. | |
| Atropine | 0.01–0.02 mg/kg as needed | IV or IM | Useful for diagnosis of reversible airway obstruction and short-term relief of bronchoconstriction. Can cause colic. | |
| Miscellaneous | Theophylline | 5–10 mg/kg q8–12 hours | Oral | Antiquated therapy. Moderate bronchodilation, variable absorption, narrow therapeutic index, frequent adverse central nervous system effects. Not recommended. |
| Pentoxifylline | 10–15 mg/kg q12 hourly | Oral | Not used clinically. Experimental evidence of efficacy. | |
| Antiinflammatory drugs | ||||
| Corticosteroids | Dexamethasone phosphate or in alcohol | 0.02–0.1 mg/kg q24 hourly | IV, IM, or oral | Effective at reducing clinical signs within 3 days. Gradually reduce dose and frequency to lowest efficacious dose. |
| Dexamethasone-21 isonicotinate | 0.04–0.06 mg/kg q3 days | IM | Effective. Infrequent dosing. | |
| Prednisolone | 1–2 mg/kg q24 hourly | Oral or IM | Effective at reducing clinical signs within 3 days. Gradually reduce dose and frequency to lowest efficacious dose. | |
| Prednisone | 1–2 mg/kg q24 hourly | Oral | Variable efficacy and not efficacious in most horses. Do not use. | |
| Triamcinolone acetonide | 0.011–0.022 mg/kg q2–4 weeks | IM, SC | Infrequent dosing and therefore lack of ability to taper dose. Should not be repeated at < 3-month intervals. | |
| Beclomethasone | 1–9 µg/kg q12 hourly | Inhalation | Relief of bronchoconstriction within 3 days. Lowest dose does not cause adrenal suppression and is effective in relief of bronchoconstriction. | |
| Fluticasone | 2–12 µg/kg q12 hourly | Inhalation | Potent and effective. Expensive. | |
| Other | Cromolyn sodium | 200 mg q12 hourly | Inhalation | Undetermined efficacy. Should be used before exposure to inciting agent. |
| Montelukast | 0.11 mg/kg q24 hourly | Oral | Leukotriene receptor antagonist. Not efficacious at this dose. |
|
Data from: Couetil, L.L. (2014) In Hinchcliff KW, Kaneps AJ, and Geor RJ (eds): Equine Sports Medicine and Surgery: Basic and clinical sciences of the equine athlete, ed. 2. Elsevier Health Sciences. p 614.