Pre-Hospital Sedation Options for Aggressive and Anxious Dogs

Kate Cummings, DVM, DACVAA
www.angell.org/anesthesia
anesthesia@angell.org
617-541-5048

Aggressive and/or fearful dogs present several challenges for the small animal practitioner. These patients are difficult to fully evaluate and present a safety hazard to the clinic staff, veterinarian, and sometimes even the owner. In addition, a nervous dog contributes to heightened stress within the work area affecting not only people but other pets alike. In dogs known to be aggressive within the hospital setting or those with tremendous fear/anxiety, making physical exams and basic assessment impossible, pre-hospital sedation can dramatically improve the experience for all involved in that patient’s care.

Before considering pre-hospital sedatives, it is imperative that the veterinarian as the prescriber has adequate knowledge of the dog’s health status and understanding of when a medication is contraindicated.¹ A full physical exam should be completed before prescribing any of the recommended medications. Additionally, each go-home medication should be discussed with the owner in terms of patient risk(s) and what to expect at home. The therapies introduced in this brief article, acepromazine, gabapentin, trazadone, and melatonin, are meant to supplement low stress handling (e.g. bringing overly aggressive dogs directly into an exam room vs. having these dogs sit in a waiting room with other stressed/vocal animals) within the clinic setting to provide a patient more amenable to handling.

Acepromazine is part of the phenothiazine class of sedatives and has widespread use within the veterinary world primarily during the perianesthetic period. Acepromazine elicits behavior-modifying effects primarily by drug binding and blockade of dopamine receptors in the basal ganglia and limbic system.^2,3 The drug exists for veterinary use in two forms – oral and injectable – and while the oral formulation has historic use in managing at home anxieties (e.g. thunderstorms, fireworks, etc.), it can be unreliable in terms of desired sedative effect and onset/duration are often variable. The injectable form, however, administered oral transmucosally (OTM) offers very reliable moderate to marked sedation within 20-30 minutes. With this route of administration, the dose closely follows recommended intramuscular (IM) dosing (Table 1).^2,3,4 In the aggressive or fearful dog, this drug is best given 30-60 minutes prior to the hospital visit (send owners home with the injectable without needle, 2 doses in case one is lost during administration attempt) and instruct that effects are most profound following absorption from the oral mucosa.  Contraindications are listed, but primarily include disease states that would deter one from using acepromazine in an anesthetic protocol (Table 1).

Gabapentin is an antiepileptic, anxiolytic, and pain management agent widely used in humans and more recently used in veterinary medicine for chronic pain therapy.^1,5 Exact mechanism of action of analgesia is unknown, but postulated due to interaction with voltage gated calcium channels.^2,3,5 In the acute setting (first one to two days of administration), sedation following gabapentin administration is often profound. This makes gabapentin an ideal agent to use alone, or often in combination with acepromazine, as part of a pre-hospital sedation protocol in the challenging dog patient. Dosing recommendations and timelines are proposed below (Table 1). Owners need to be made aware that their pet will often appear considerably more sedate at home. Supervision on stairs and getting into and out of the car should be recommended to clients with gabapentin alone or in combination with other sedatives.

Trazodone is classified as a serotonin receptor antagonist and reuptake inhibitor (SARI),^2,6,7 used primarily in the acute hospital setting to manage anxious patients⁶ as well as long term as a single or adjunctive agent in dogs with anxiety disorders.⁷ While trazodone has a large safety profile, it should be used with caution in patients with known arrhythmias as serotonergic medications may increase the heart’s arrhythmogenic potential.⁸ Onset of action is approximately one hour and the dose range can be large for this medication (Table 1), but for the purposes of pre-hospital sedation, it is recommended to start at 5 mg/kg.

Melatonin, the naturally occurring hormone produced by the pineal gland, is available as a neutroceutical in dogs (http://www.lignans.net/melatonin1.html). While melatonin has proven beneficial in the management of certain endocrine disorders, it is a helpful adjunct in canine stress disorders. Therefore, melatonin is offered as an over-the-counter recommendation for the dog with hospital associated aggression and anxiety (Table 1).

Table 1: Dosing and timeline of administration for sedative agents.

*Timing recommendations based on morning appointments. If appointment falls in afternoon or evening, morning administered medications are likely to have little effect. Timing regimen should be adjusted based on dog’s appointment time.

While all of these medications can be given as single agents, it is recommended to combine in a stepwise process until desired sedation is achieved. The combination of gabapentin and acepromazine is often very effective in the aggressive and/or fearful patient, allowing one to safely muzzle, place an E-collar, or administer additional IM sedation without causing large undue stress to the dog or hospital staff. If additional at-home sedation is desired though, melatonin, and then trazodone can be considered.

When sending home pre-hospital visit sedation with owners, it is important to do a trial of the sedation before the event so owners have an idea of what to expect. It is very common that the dog appears much more sedate at home in comparison to the clinic and duration of sedation can be variable – up to 24 hours, which is normal and not harmful. Practice and learned comfort with oral sedation can dramatically improve the hospital experience for stressed and fearful dogs, but requires self-, client-, and staff-preparedness in mitigating additional stressors within the hospital environment. The outcome is a dog that adapts more readily to a new environment, allowing for an improved patient assessment and patient-doctor relationship.

References:

1. The Chill Protocol, Karas AM. Personal Comm.
2. Lumb and Jones’ Veterinary Anesthesia, 4^th Thurman JC, Tranquilli WJ, Benson GJ. Baltimore: Williams & Wilkins; 2007.
3. Essentials of Small Animal Anesthesia and Analgesia, 2^nd Grimm KA, Tranquilli WJ, Lamont LA. Wiley-Blackwell; 2011.
4. Handbook of Veterinary Anesthesia, 5th Edition. Muir WW, Hubbell JAE, Bednarski R, and Lerche P. St. Louis: Mosby; 2013.
5. Lamont LA. Adjunctive Analgesic Therapy in Veterinary Medicine. Vet Clin: SA Prac 2008;38:1187-1203.
6. Gruen ME et al. The Use of Trazodone to Facilitate Post-Surgical Confinement in Dogs. J Am Vet Med Assoc 2014;245(3):296-301.
7. Gruen ME and Sherman BL. Use of trazodone as an adjunctive agent in the treatment of canine anxiety disorders: 57 cases (1995-2007). J Am Vet Med Assoc2008;233(12):1902-1906.
8. Horwitz D, Neilson J. Pharmacology. In: Blackwell’s Five-Minute Veterinary Consult: Clinical Companion (Canine and Feline Behavior). Blackwell Publishing; 2007.
9. James SP and Mendelson WB. The Use of Trazodone as a Hypnotic: A Critical Review. J Clin Psychiatry 2004;65(6):752-755.