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Treating Albuterol Toxicity

By Sara Doyle, DVM
angell.org/emergency
sdoyle@angell.org
617-541-5121

 

Toxin ingestion is a common presenting complaint among pets in the emergency room, and of all those incidents, according to the ASPCA Animal Poison Control Center, the most commonly reported is ingestion of human medications. Albuterol ingestion and resulting toxicity is somewhat uncommon, and unlike with the more frequently occurring chocolate or grape toxicity, a veterinarian faced with this situation may not immediately know how to proceed. A retrospective study on this subject was recently published in the Journal of Veterinary Emergency and Critical Care by veterinarians from the Angell Emergency and Critical Care service. This study outlined the pathophysiology, treatments and outcomes for thirty six dogs who presented through the emergency service for albuterol toxicosis. The fortunate news for our patients and their owners is that most dogs tend to do very well with prompt supportive care and for a relatively short duration of hospitalization.

Albuterol Pharmacokinetics

Albuterol is used as a human (as well as a veterinary) treatment for asthma. It acts as a selective β2-adrenergic receptor agonist to provide bronchodilation by relaxing smooth muscles in the bronchi. It is short-acting and considered effective for quick relief of symptoms of bronchoconstriction, although it does not relieve long-term inflammation of the airways due to the underlying disease processes. Albuterol and other β2 agonists also cause transient hypokalemia and hypophosphatemia via an unknown mechanism, although both of these are due to intracellular shifts of these ions rather than overall depletion. One hypothesis is that stimulation of the Na-K-ATPase pumps causes intracellular influx of potassium. In addition to its primary purpose of bronchodilation, albuterol also causes peripheral vasodilation and cardiac stimulation. Paradoxical bronchoconstriction has also been reported, as well as exacerbation of asthma symptoms in patients taking large qualities of β2 agonists. The shifts in potassium can also cause cardiac arrhythmias including ventricular arrhythmias due to delayed repolarization of the myocardium. These mechanisms can, of course, be life-threatening if not identified and addressed promptly.

Presentation

The route of exposure for the veterinary patient depends on the prescribed form of the albuterol. In all species, including humans, it is most commonly prescribed as an aerosol in a canister which when punctured immediately delivers a dose via inhalation or exposure through the mucus membranes. Asthma inhalers often contain up to 200 intended doses, depending on brand and number of previous uses.  If a canister is chewed and punctured, it can potentially administer a severe overdose in a very short period of time. Ingestion of an oral form of the medication is another possible route of exposure. The clinical signs most commonly seen include sinus tachycardia, tachypnea, lethargy and vomiting (see Figure 1). Signs such as collapse and death have also been reported, but this is very uncommon. Patients often appear agitated or, conversely, lethargic. On intake to the hospital they may also be noted to have hypertension or hypotension. Often, exposure to albuterol is documented by the owners, but in the absence of this a full history of potential toxins in the household should be taken.

Figure 1: Retrospective evaluation of albuterol inhalant exposure in dogs: 36 cases (2007-2017). Meroni, Emiliana R. et al. Journal of Veterinary Emergency and Critical Care. 2020; 1-8.

 

Treatment and Monitoring

It is not recommended to induce emesis unless the patient ingested albuterol pills. With the more common method of inhalation or solution ingestion, the focus is instead placed on cardiovascular and electrolyte support for the duration of clinical signs (usually up to 12 hours). In the case of ingestion of pills, activated charcoal decontamination can also be implemented. On intake, a minimum database that includes serum potassium, phosphorous and glucose should be performed. Some publications also advise measurement of cardiac troponins to assess for myocyte damage.

If admission to a hospital is possible, intravenous fluid therapy should be implemented for cardiovascular support. Potassium supplementation should be started if hypokalemia is noted. Propranolol, which acts as a non-selective β-blocker, can be used as a specific antagonist to treat the tachycardia and should be administered intravenously at 0.02-0.06mg/kg every 8 hours to effect. To control hypertension, esmolol (loading dose of  50–200mcg/kg IV slowly to effect over 1–2 minutes, then 50–200mcg/kg/min as needed) or metoprolol (0.5mg/kg every 12 hours) can be considered as a more specific β1-blocker. While ventricular arrhythmias were seen in only one patient during the retrospective study mentioned earlier, they have been reported throughout the literature and lidocaine can be administered to control these should they arise. Electrocardiogram monitoring for heart rate and rhythm should be strongly considered, and monitoring of serum potassium and phosphorus should be performed every 4-6 hours for 12 hours.

Figure 2: https://www.petpoisonhelpline.com/poison/asthma-inhaler/

 

If admission to the hospital is not possible for financial or other reasons, the patients who participated in the study as outpatients were still found to have a favorable outcome, with all of them surviving the event. If resources permit, at least a brief EKG and basic electrolyte screening panel should be performed. Subcutaneous fluids should be administered for support, and if potassium on intake is found to be low, oral supplementation can be implemented for three days duration. Tachycardia can be controlled with oral administration of the β-blocker atenolol (0.2-1.0mg/kg every 12-24 hours) for the same three days duration. Ideally, blood work would be rechecked the next day to ensure that electrolyte normalcy has been achieved.

Prognosis

The recent retrospective study showed a good outcome for all 36 dogs included, both those who underwent inpatient and outpatient management. While the average hospital stay for those who were managed as inpatients was around 20 hours, most patients who can be supported through the first 12-18 hours will not have residual signs. However, patients reported to develop arrhythmias or who may have already had underlying cardiac disease are at a higher risk and the prognosis may be more guarded in these cases. By taking a complete history, basic diagnostics, and symptomatic care, a positive outcome is usually achieved.

 

References

  1. How to Treat Albuterol Ingestion. ASPCApro. Accessed at https://www.aspcapro.org/resource/how-treat-albuterol-ingestion.
  2. Toxicology case: Albuterol toxicosis in a pit bull terrier. Sobczak, Brandy R. DVM360. March 1, 2015. Accessed at https://www.dvm360.com/view/toxicology-case-albuterol-toxicosis-pit-bull-terrier.
  3. Retrospective evaluation of albuterol inhalant exposure in dogs: 36 cases (2007-2017). Meroni, Emiliana R. et al. Journal of Veterinary Emergency and Critical Care. 2020; 1-8.
  4. Top 10 animal toxins of 2016. ASPCApro. Accessed at https://www.aspcapro.org/resource/top-10-animal-toxins-2017.
  5. Bronchodilators. Rosendale, M. Clinical Veterinary Toxicology. 2004: 305-307.
  6. Asthma Inhaler. Pet Poison Helpline. Accessed at https://www.petpoisonhelpline.com/poison/asthma-inhaler/.
  7. Inhalation Therapy of Airway Disease. Dowling, Patricia M. Merck Veterinary Manuel. October 2014. Accessed at https://www.merckvetmanual.com/pharmacology/systemic-pharmacotherapeutics-of-the-respiratory-system/inhalation-therapy-of-airway-disease.
  8. Cardiovascular Drugs. Bonagura, John D. and Schober, Karsten E., Saunders Manual of Small Animal Practice (Third Edition). 2006