Targeted Medical Therapy for Respiratory Conditions in Horses
Inhaled medications benefit horses, minimize side effects
By Stacey Oke, DVM, MSc
The horse’s respiratory tract is designed to move large volumes of air to and from their lungs. During exercise, air flow rates reach a staggering 65 litres per second, which is truly amazing considering a human athlete’s flow rate is a mere four litres per second! Any abnormality of the respiratory tract that impedes airflow will decrease the volume and/or rate of oxygen being delivered to the lungs. In exercising horses, even the smallest decrease in oxygenation can have profound, negative effects on performance.
Airway Disease and Poor Performance
Dorsal displacement of the soft palate, arytenoid chondritis, upper respiratory tract infections, and equine asthma can all contribute to poor performance. Despite being clearly unique entities on paper, differentiating between upper respiratory tract disorders can be challenging.
Your veterinarian may “scope” your horse to directly visualize the structure and function of the nasopharynx, larynx, and trachea, and collect samples of tracheal mucous. They may also perform a lung wash (bronchoalveolar lavage or BAL) to evaluate the number and types of inflammatory cells present in the lower respiratory tract that the scope can’t reach.
Treatment will vary markedly depending on the underlying etiology. For structural issues surgery may be indicated, bacterial infections may require antibiotics, and anti-inflammatories and bronchodilators administered for equine asthmatics.
Choose Your Weapon
Systemically administered medications may cause serious side effects. Antibiotics can disrupt the intestinal microbiome causing diarrhea, which puts horses at risk of developing laminitis — a life-threatening inflammation of the horse’s feet. Oral or injectable corticosteroids and bronchodilators can also result in untoward reactions, especially when used long-term. Systemic bronchodilators can cause heart rate elevations, excitement, excessive sweating, and decreased gastrointestinal motility (and colic). Systemic corticosteroids may induce laminitis or suppress the hypothalamic-pituitary-adrenal axis resulting in immunosuppression.
Equine experts now support inhalation therapy for certain respiratory conditions. This involves administring aerosolized drugs directly to the airways for “topical pulmonary therapy” to maximize drug delivery to the target site while limiting side effects. Inhaled medications may also have a more rapid onset of action compared to systemic drugs and could allow for a shortened drug withdrawal time prior to competition (discuss this aspect of therapy with your veterinarian).
Managing Equine Asthma
Inhalation therapy is widely advocated for horses with equine asthma — an inflammatory airway condition characterized by coughing, mucous accumulation, and poor performance. According to the current treatment guidelines for equine asthma, affected horses should be managed using a combination of the following:
- Environmental management to keep the two-foot sphere around your horse’s muzzle clear of aeroallergens.
- Corticosteroids to decrease inflammation in the airways and rapidly improve lung function.
- Bronchodilators for reducing airway hyperresponsiveness caused by constriction of the smooth muscles that line the airways.
A number of other medications may help asthmatic horses, including mast cell stabilizers (cromones) and mucolytics (saline, acetylcysteine). Studies examining lidocaine, specific essential oils, and chelated silver are underway but data from controlled trials are currently unavailable.
Particle Size Matters
One of the keys to successful inhalation therapy is ensuring that drug particles measure a maximum of five microns in diameter. Particles larger than five microns will not reach the lower airways. Larger particles will be ineffective, an unnecessary expense, delay institution of appropriate therapies, and can even be swallowed by the horse resulting in the side effects we were trying to avoid.
Flexineb® is a portable, silent, easy-to-use nebulizer that aerosolizes liquid medications via vibrating mesh technology. Studies show that up to 71 percent of the medications nebulized by this medical device measure five microns or less, which means the drug reaches the lower airways for maximal effect. When used in clinical trials, the Flexineb® device was well tolerated by horses. This device can also be used with metered dose inhalers, such as fluticasone/salmeterol, budesonide, or ciclesonide. Maximal Flexineb® benefit will only be achieved with proper fitting and maintenance.
Medications Available for Nebulization
- 0.9% saline solution
Contact Sarah Lauren Scott, Sales Manager, Nortev Canada, for information on how to incorporate Flexineb® into your program.
Sarah Lauren Scott, Sales Manager, Nortev Canada: email@example.com, (905) 875-5876