Bigstock One of the more challenging aspects of heartworm treatment for dog owners is the need to implement strict activity restrictions before, during, and after adulticide therapy. The American Heartworm Society (AHS) guidelines recommend activity restriction begin for heartworm-positive dogs at the time of diagnosis and continue until six-eight weeks after the last melarsomine injection.1 The goal of this activity restriction is to reduce the inflammation caused by worm death and reduce adverse events, such as pulmonary thromboembolism. Unfortunately, activity restriction is often easier said than done, and compliance can depend heavily on the dog, the owner, and their lifestyle. At the onset, it is important to have an open conversation with clients about what they can manage for their dogs to stress the importance and justify the recommended activity restriction. Lessons in longer-term confinement and activity restriction can be taken from animal sheltering, where we are challenged with the prolonged confinement and behavioral welfare concerns it poses to dogs in general, and especially those undergoing treatment. When approaching a dog’s medical and behavior needs holistically, we consider whether environmental, behavioral, or pharmaceutical modifications can be made. Like other multimodal treatments, the more elements we can modify and the more tools we give owners for success, the more successful we can be with our patients.2 Environmental modification Historically, this might have meant “crate rest” or significant confinement during the treatment period. While this may be the most appropriate way to restrict activity for some dogs—particularly those accustomed to crating—crate confinement is not appropriate for a dog unaccustomed to crating that will panic and exert excess activity trying to escape. Not only would this negate the purpose of activity restriction and put the patient at a higher risk of complications, but the dog could injure itself. Furthermore, owners are unlikely to be compliant if the dog appears to be in distress. An open discussion with the owner about their dog’s general lifestyle and activity level, as well as what changes can feasibly be made to reduce their activity, is essential.3 If the owner makes it clear that leaving their dog alone in a crate is unsafe or impractical, a viable alternative is to ask the owner to identify a room in the house where the dog will stay. If the room chosen has a window that gives the dog visibility outdoors, discuss with the owner whether the dog is likely to get excited and bark. If so, recommend temporary window covers to prevent this behavior and excitement. A translucent window cling can be applied to block sight outside and prevent excitement and barking during activity restriction. Photo courtesy Dr. Uri Donnett Environmental modification also includes short, controlled leash walks instead of free yard time or going for long walks or jogging for bathroom breaks.4 It is also important to think about what can be added to the environment as enrichment vs. telling the owner what they must take away from the dog. While food or treats can be great motivators, there is a fine balance here between providing food enrichment and allowing weight gain during restriction. Stress to owners the need to avoid increasing their dog’s caloric intake and, instead, suggest creative alternatives, such as feeding their dog’s kibble allowance in puzzle toys or snuffle mats.5 Another alternative is to portion a small amount of the dog’s kibble with a little wet food inside a chew toy for added enjoyment and doggie distraction; it could also be frozen. Alternative enrichment options can include providing auditory, olfactory, and visual enrichment. Playing classical music or audiobooks during periods of greater restriction may help with restful behavior. Pheromone sprays or collars may also assist with calming. Food is hidden inside the folds of a snuffle mat slowing eating and providing enrichment during meal time. Photo courtesy Dr. Uri Donnett Behavioral modification Generally, we think of behavior modification as the use of training tools to change a dog’s behavior and emotional responses. In cases of activity restriction, we want to use these tools to ensure the dog maintains a positive emotional state and to address any fear, anxiety, stress, or frustration that may develop. If a dog is going to be - or kennel-confined, behavior modification and training can be used to crate-train the dog and position the crate as a safe and positive environment. YouTube has a wide variety of videos on crate rest activities. Recommend that clients research these and find enrichment strategies that suit their dog. Likewise, a very active dog might struggle on short leash walks. Playing training games, distracting with treats, and avoiding exciting stimuli will all help make these potty breaks more successful and less arousing.4 Instead of punishing a dog with a long period of activity restriction, invite owners to see this time as a way to bond with their dog in other ways. Training new tricks or skills will keep the dog mentally engaged and strengthen the bond between owner and pet. Learning to sit, lay down, and stay, are just the beginning of the skills an owner could train. YouTube can also be a useful resource for finding videos for home training tips. Owners should look for training videos that focus on positive reinforcement methods. Psychopharmaceuticals We now have several psychopharmaceutical drugs that can be useful in reducing the fear, anxiety, and stress that can be triggered by prolonged activity restriction. These medications are commonly used in animal sheltering to assist dogs with acute situational stress from kenneling and can be just as useful in a home environment.6 It is important to note pharmaceuticals should be used in conjunction with environmental and behavior modifications to achieve the best possible outcome for each patient. When choosing a drug, the prescriber should also consider the time to take effect, duration, and potential side effects. In the case of activity restrictions for heartworm disease, we need a drug that will take effect quickly, have sufficient duration for a reasonable owner to re-dose the medication, and have minimal cardiovascular side effects. The most commonly used drugs that fit these needs include trazodone, gabapentin, and benzodiazepines. All uses of the drugs described below are extra-label: Trazodone Trazodone is a serotonin antagonist and reuptake inhibitor. It has a wide dosage range (3-15 mg/kg BID-TID) and is generally well tolerated by patients. Effects from trazodone can be seen within 30-45 minutes and can last eight-12 hours.8 The most common side effects include GI upset, sedation, ataxia, appetite changes, and agitation. Starting at a lower dose and then increasing after a few days can help to avoid GI side effects in some dogs. A study evaluating trazodone for confinement post-orthopedic procedures found that owners reported the intensity of greeting and overall calmness of the dogs was significantly improved.7 A recent study of trazodone at 10 mg/kg evaluating cardiovascular effects found a mild decrease in blood pressure but not clinically relevant cardiovascular changes and the drug was well tolerated.9 Gabapentin While the mechanism of action of gabapentin is not entirely understood, it has anticonvulsant, analgesic, and anxiolytic properties reported in dogs.10 Gabapentin also has a wide dosage range, with dosages from 10-30 mg/kg BID-TID commonly reported. A recent study of gabapentin at 30 mg/kg evaluating cardiovascular effects did not find any clinically relevant cardiovascular changes, and the drug was well tolerated.11 Common side effects of gabapentin include sedation and ataxia. It is important to note some formulation of liquid gabapentin contains xylitol and should be avoided. Gabapentin is also a controlled drug in some jurisdictions. Benzodiazepines This class of drugs has an inhibitory action on the central nervous system and is generally used for anxiety and phobia disorders. The duration of action depends on the drug, but can last from three to 10 hours, and they generally have a rapid onset of action. It is important to note that all drugs in this class are controlled substances, and longer-term use in dogs can cause physiologic dependence. Side effects include anxiety, hallucinations, polyphagia, sedation, and paradoxical excitation, which would not be desired in a dog with activity restriction. Additionally, these drugs can cause behavioral disinhibition and may not be appropriate to use in dogs with histories of aggressive behavior. Benzodiazepines are also generally safe to use in combination with other medications and have minimal cardiovascular effects when used at appropriate doses. Alprazolam is the drug from this class that would most commonly be used at a dose range of 0.02 to 0.04 mg/kg BID.8 In summary, activity restriction is one of the most important ways to ensure your patients experience safe heartworm treatment and avoid complications. Approaching activity restriction holistically and recommending a plan that incorporates environmental, behavioral, and pharmaceutical interventions can help improve client success andcanine welfare. Uri Donnett, DVM, MS, DABVP (Shelter Medicine Practice), is chief veterinarian at the Dane County Humane Society in Madison, Wis. He currently serves as secretary-treasurer on the board of directors for the American Heartworm Society. References Heartworm Guidelines. American Heartworm Society. https://www.heartwormsociety.org/veterinary-resources/american-heartworm-society-guidelines Exercise Dos and Don’ts during Heartworm Treatment. https://d3ft8sckhnqim2.cloudfront.net/images/infographics/Exercise_Dos_Donts_02JAN2023.pdf?1764662060 DiGangi, Brian. Taking on Tough Questions FAQ. https://d3ft8sckhnqim2.cloudfront.net/images/DiGangi_exercise_restriction.pdf?1653686741 Horwitz, Debra. Handling bathroom breaks for dogs on cage rest. https://www.youtube.com/watch?v=jQJo19N7gJY Horwitz, Debra. Keeping dogs mentally stimulated but physically quiet during heartworm treatment. https://www.youtube.com/watch?v=LjX-QnxBD6E Xue J, Fuller E, DiGangi B, Donnett U. The American Heartworm Society and Association of Shelter Veterinarians’ 2024 Shelter Heartworm Management Practices Survey Gruen ME, Roe SC, Griffith E, et al. Use of trazodone to facilitate postsurgical confinement in dogs. J Am Vet Med Assoc 2014; 245:296-301. Erickson, Amelia, et al. “A review of pre-appointment medications to reduce fear and anxiety in dogs and cats at veterinary visits.” The Canadian Veterinary Journal9 (2021): 952. Quigley LE, Bain M, Lenske E, Fine J, Ren Y, Gagnon A. Hemodynamic, Echocadiographic, Electrocardiographic, and Behavioral Effects of Oral Trazodone in Healthy Dogs. 2024 ACVIM Forum Research Report Program, Journal of Veterinary Internal Medicine, Volume 38, Issue 5, September-October 2024, Pages 2823–28394. Di Cesare, Federica, et al. “Gabapentin: clinical use and pharmacokinetics in dogs, cats, and horses.” Animals12 (2023): 2045. Lenske E, Gagnon A, Nakonechny L, Wilson M, Bain M. Hemodynamic, Echocadiographic, Electrocardiographic, and Behavioral Effects of Oral Gabapentin in Healthy Dogs. 2024 ACVIM Forum Research Report Program, Journal of Veterinary Internal Medicine, Volume 38, Issue 5, September-October 2024, Pages 2823–28394.
