Investigation of Neurokinin-1 Receptor Antagonism as a Novel Treatment for Chronic Bronchitis in Dogs
M Grobman, and C Reinero
JVIM 2016; 30: 847-852. Summarised by Mirinda van Schoor
Why they did it:
Canine Chronic Bronchitis(CCB) is defined as a self perpetuating inflammatory disease of the airways in dogs. It is characterized by the presence of a cough of more than 2 month’s duration in patients for which cardiac disease and other respiratory causes of coughing were excluded.
The only effective therapy in CCB cases is the lifelong administration of corticosteroids. Substance P and its receptor, neurokinin-1 (NK1-R), have been implicated in peripheral and central sensitization of the cough reflex, as well as in the exacerbation of airway inflam-mation via their role in the recruitment of airway leu-kocytes.
Maropitant (Cerenia®, Zoetis) is an NK-1 receptor an-tagonist which has been anecdotally reported to de-crease the frequency of coughing in dogs with CCB. It was hypothesized that maropitant will decrease both coughing and airway inflammation in dogs with CCB, making it the perfect alternative to corticosteroid ther-apy.
What they did:
Eight client-owned dogs were treated with maropitant at the recommended dose of 2mg/kg once daily. This dose was given on alternate days in order to decrease any side effects that may be associated with chronic treatment. The drug was administered for a period of 2 weeks to ensure that a steady state concentration was reached. Steady state is achieved after 4 doses. The owners were given surveys to complete, together with visual analogue scales to measure clinical signs prior to enrolment, after 1 week of therapy and after 2 weeks of therapy. Airway samples for cytology were collected via bronchoalveolar lavage prior to treat-ment and again after 2 weeks of treatment. None of the dogs were given corticosteroids, antibiotics or an-titussives during the study period.
What they found:
All owners reported significant clinical improvement in their pets’ condition and agreed that maropitant was an acceptable long term treatment for CCB. Clients reported 75% decrease in cough frequency and 88% decrease in cough severity. Only one owner reported adverse effects (decreased appetite and activity), but these were not severe enough for the owner to con-sider discontinuation of the drug.
Airway cytology revealed no significant difference in the percentage of inflammatory cells (neutrophils or eosinophils) between the time of enrolment and after 2 weeks of treatment. This finding renders maropitant unsuitable as a monotherapy drug in the management of CCB.
Take home message:
Although maropitant decreased frequency and sever-ity of coughing in CCB, it did not have a significant effect on airway inflammation. Because the control of airway inflammation is paramount in the management of CCB, maropitant cannot be recommended in the treatment of CCB. However, it’s role as an antitussive in other diseases such as tracheal collapse warrants further investigation.