By Stephanie Davis, DVM
Owner & Sport Horse Veterinarian, Davis Equine;
Barn Manager - The Plains, VA
We have previously discussed several uses for the Flexineb® nebulizer. What we haven’t discussed is how important it is to know WHY we want to nebulize medication in the first place. Before the invention of the equine nebulizer, the medications available were administered systemically. So, why do we even need the nebulizer if we can just inject intravenous or intramuscular? Two main reasons; First, and simply, inhalation (nebulization) delivers a high concentration of drug directly where it is needed in the lung. Second, achieving a similar concentration of medication in the lung by systemic administration requires the entire body to be exposed to relatively high concentrations of drugs that can cause serious side effects.
There are two main groups of drugs that are commonly used with airway conditions, bronchodilators and corticosteroids. Corticosteroids are very potent anti-inflammatory drugs that essentially suppress every part of the inflammatory process. This suppression makes them very effective, but because their pharmacologic and physiologic effects are so broad, the potential for negative side effects is considerable. Corticosteroids are excellent for nebulization because of the large number of glucocorticoid receptors on the cells of the lining of the airway. As mentioned above, it is ideal to deposit the medication where it is needed to decrease the likelihood of side effects. Some side effects of prolonged systemic corticosteroid use include laminitis and enhanced susceptibility to infection. These side effects have not been found when administering corticosteroids by inhalation. So, consider the ever so common laminitic pony that needs respiratory treatment. This pony is more susceptible to the effects of the systemic corticosteroids and would have to be treated by nebulization to reduce the chance of a laminitic episode.
Bronchodilators are used to alleviate obstruction caused by smooth muscle contraction in the airway and also help to clear mucous from the airway. They are often used alongside corticosteroids as they don’t address the inflammation, but only associated clinical signs (cough and mucous production). There are two classes of bronchodilators. They are anticholinergics and beta 2 adrenergic agonists. The beta 2 agonists (clenbuterol) are used more often as the anticholinergics have higher risks of complications including tachycardia (increased heart rate) and ileus (a slowing of the movement of the GI tract). Ileus is one of the biggest concerns as horses have the unique need to have the GI tract moving at all times. Ileus can quickly lead to colic, which is a serious complication when your intent was to only treat respiratory disease.
Although all of the above medications are used daily with little to no problems, there are serious risks to consider. These complications are typically avoided because the veterinarian has already considered the risks of the individual patient and has chosen lower doses or the use of nebulization to reduce the chance of serious side effects such as laminitis and colic. There is much to be considered when developing a treatment protocol. The age, breed, predisposition (laminitic pony), and many other factors can be important in the recovery of each individual horse’s condition. The Flexineb® is an easy to use tool that can lower those risks and make it easy to develop a safe protocol for almost any horse. As always, we encourage you to consult with your treating veterinarian prior to the use of the Flexineb® equine nebulizer.
Published December 2014.