Today's Veterinary Practice

MAR-APR 2018

Today's Veterinary Practice provides comprehensive information to keep every small animal practitioner up to date on companion animal medicine and surgery as well as practice building and management.

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PEER REVIEWED 20 NUTRITION NOTES Tetrahydrocannabinol (THC) A synthetic form of TCH (dronabinol) is used in people for appetite stimulation. It also has anti-emetic and anti-nausea effects. The dose in dogs and cats is unclear, and there is limited information regarding effectiveness in companion animals. There is a risk of toxicity with this drug, and it is a Class III-controlled drug. Glucocorticoids These drugs stimulate appetite via increasing neuropeptide Y and decreasing pro-inflammatory cytokine production. Many dogs will increase intake while receiving glucocorticoids, but cats are relatively resistant to their appetite stimulating effects. Side effects are substantial, with muscle wasting, delayed healing, immunocompromise and diabetes mellitus. As a general rule, steroids should not be given to an anorexic animal prior to establishing a definitive diagnosis as these drugs will hide lymphoma but let infectious agents such as Histoplasma run rampant. Capromorelin (Entyce®) This drug is currently approved for use in dogs and is the first ghrelin receptor agonist approved for use in veterinary medicine. A feline product is also in development. Safety and field studies indicate that this drug is a potent appetite stimulant, with a wide safety margin. This drug is likely to have wide applications for the management of both transient and sustained hyporexia in companion animals. In addition to stimulating the orexigenic neurons and promoting food intake, ghrelin also triggers the release of growth hormone (GH) from the pituitary. This supports muscle growth along with weight gain. Negative feedback from insulin-like growth factor-1 limits GH production so that levels remain robust but are not excessive. Numerous ghrelin receptor agonists are under investigation for use in people. Preliminary data shows substantially longer survival times in patients with metastatic neoplasia, mitigation of gastroparesis in those with Parkinson's disease, and beneficial anti-inflammatory effects. This drug class offers substantial promise in the management of various conditions in both human and veterinary medicine. Feeding tubes There are numerous options for assisted parenteral feeding using food delivery tubes. Some can be placed in awake patients with minimal or no sedation (nasoesophageal, nasogastric, nasojejunal), while others require general anesthesia (esophageal, gastric, gastrojejunal, jejunal). As a broad guideline, I use nasal tubes for transient support, as these are often uncomfortable and should be regarded as a temporary bridge to self-feeding or placement of another device when the patient is stabilized. I tend to place a longer-lasting feeding tube pretty promptly in my patients (particularly cats), and generally chose an esophageal tube. These can be placed very quickly and are well-tolerated, but the patient must be under anesthesia with an endotracheal tube in place. SUMMARY Managing hyporexia can be challenging and a multimodal approach is often needed. Pharmacological agents can play a key role in improving intake, and the new ghrelin agonist drugs show tremendous promise in this regard. Although the consequences of prolonged inadequate intake may be insidious, dysrexia can markedly impact patient outcomes and must be promptly addressed. Recommended Reading 1. Ferguson LE, McL ean MK, Bates JA, Quimby JM. Mirtazapine toxicity in cats: retrospective study of 84 cases (2006-2011). J Fel Med Surg 2015; 10.1177/ 1098612X15599026 2. Genton L, Cani PD, Schrenzel J. Alterations of gut barrier and gut microbiota in food restriction, food deprivation and protein-energy wasting. Clin Nutr 2016;34: 341-349. 3. Quimby JM, Lunn KF. Mirtazapine as an appetite stimulant and anti-emetic in cats with chronic kidney disease: a masked placebo- controlled crossover clinical trial. Vet J 2013;197:651-655. 4. Zollers B, Allen J, Kennedy C, Rhodes L. Capromorelin, an orally active ghrelin agonist, caused sustained increased in IGF-1, increased food intake and body weight in cats (Abstract) Proceedings of ACVIM Forum 2015. Audrey K. Cook Audrey K. Cook is a Diplomate of both ACVIM and ECVIM and is Board Certified in Feline Practice (ABVP). She is currently an associate professor of small animal internal medicine at Texas A&M, with particular interests in endocrinology, gastroenterology, feline medicine and endoscopy. Dr. Cook routinely speaks at national meetings and is a recipient of the Texas A&M University Distinguished Achievement Award in Teaching.

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