VETTALK Volume 15, Number 04 American College of Veterinary Pharmacists THE HARD TRUTH ABOUT PROKINETIC MEDICATION USE IN PETS Introduction Pathophysiology/Etiology to that observed in dogs. It can be The moving topic of this Vet Talk As with most diseases in the veteri- due to a trichobezoar, dehydration, newsletter will be prokinetic medica- nary world, the etiology and patho- obesity, old age, diabetes, immobility, tions. The availability of information physiology of constipation are varied pain from trauma to the low back, on the many prokinetic agents is var- depending on the species being dis- bladder infection, or an anal sac infec- ied at best so an overall consensus of cussed, where in their gastrointestinal tion. In cases that are more chronic, prokinetic medications will be as- tract the problem is occurring, and underlying disease such as colitis or sessed in this article, hopefully giving any accompanying comorbid condi- Irritable Bowel Syndrome (IBS) may better insight to practitioners about tions. be the culprit. On the other hand, the which agents to use in their patients. cause may be idiopathic which is Canines: In man’s best friend, consti- frustrating for both veterinarian and Prevalence pation has many origins. A dog’s patient since this form is most diffi- Chronic constipation and gastroin- digestive tract itself is complex but cult to treat. testinal stasis are highly debilitating ultimately the mass movements and conditions that not only affect human haustral contractions from the large Equines: Despite their large size, patients but our four legged patients intestine (colon), propel feces into the horses have incredibly delicate diges- as well! Though this condition is rectum stimulating the internal anal tive systems. Their stomach is rela- equally widespread amongst our nu- sphincter to relax. This then signals tively small compared to their body merous veterinary species, there are a the diaphragm and abdominal mus- size which then passes food through few specific groups who are more at cles to contract increasing pressure approximately 100 feet of digestive risk. For example, prevalence of con- while the external anal sphincter re- tract to include the small intestine, stipation is higher in the following laxes resulting in defecation. How- then cecum, large colon, small colon, dog breeds: English Bulldogs, Boston ever, various factors can impede this and finally rectum. Terriers, and German Shepherds. multifaceted process. Such examples During times of illness or stress Cats who are most affected include include ingesting foreign objects (i.e. horses may stop eating, drinking, and Siamese, Domestic Shorthair, and socks, garden hoses, shoes), anal sac Manx as well as those cats who are inflammation, long term opioid use middle-aged and male. Horses, rab- (i.e.tramadol), chemotherapeutic bits, guinea pigs, and chinchillas may medications (i.e.vincristine), obesity, also experience various forms of con- old age, immobility, and dehydration. stipation due to their unique digestive However, other more severe underly- systems. ing physiologic etiologies such as neuromuscular disease, diabetic gas- troparesis, or a neoplastic gastrointes- tinal obstruction may also be attribut- able to GI stasis. Felines: Cats can also develop con- stipation from several causes as their process of defecation is fairly similar with all of the aforementioned rea- Summary of Clinical Signs can develop colic which even in the sons, will surely result in a final out- 1. Increased tenesmus mildest form, results in pain, abnor- come of poor gastric motility 2. Failure to defecate mal motility, and even ileus. Colic 3. Fecal matter, if passed, is reduced has many origins but the forms most Rodents: Guinea pigs and chinchillas in quantity and is usually dry and likely to cause constipation are im- have a high metabolic rate, a hard paction colics due to fecal material, monogastric stomach, and an impres- 4. Presence of blood in stool parasites, or enteroliths. Other causes sive cecum that is so large it takes up 5. Feces that are particularly foul for gut immobility include pelvic approximately ½ of their body cavity. smelling flexure impaction from food, poor In the cecum, much like in horses and 6. May continuously get in and out food quality, an inability to access rabbits, there is fermentation by key of litter box without passing fecal free forage, dehydration, severe hind microflora. If their diets aren’t main- material limb pain or injury, or long term use tained appropriately with high fiber 7. Circling or pacing the stall with of anticholinergic medications such and low carbohydrates (similar to intermittent straining as atropine. lagomorphs), dysbiosis occurs result- 8. Decreased activity and lethargy ing in GI distress. Other reasons for likely due to pain constipation include dehydration, old 9. Painful and/or bloated abdomen age, spinal pain, obesity, excess fatty 10. Decreased interest in food diet, a lack of exercise, and dental 11. Irritability disease than can severely impair eat- ing and drinking. Diagnosis The primary means of diagnosing Clinical Signs and Symptoms any species with gastrointestinal sta- The classical clinical sign of consti- sis is through a complete history, pation is straining to defecate without thorough physical exam, and careful production of feces, droppings, or observation of their patient’s behav- manure. Affected animals can be of ior. A CBC and Chemistry Panel will Lagomorphs: Rabbits and hares have either sex, although in cats there is a be useful for identifying and/or ruling digestive systems that resemble male predilection, and of any age out other disease processes such as horses, rather than dogs or cats. Per- though often younger or older ani- diabetes, pancreatitis, or an underly- haps it is for this reason that they too mals are most affected. Besides ing infection. Abdominal radio- are very prone to GI stasis. The tran- straining, there may also be signs of graphs and ultrasounds both present sit time of the small intestine is rapid, general discomfort, irritability, a de- the practitioner with an even better and fibrous material is quickly moved crease in appetite, and a frequent understanding to what is, or is not, to the cecum and large intestine. need to want to defecate with postur- palpated on physical exam. It is very The cecum is where fermentation by ing and lifted tail. Variations of these important to discuss with the owner bacteria occurs. Indigestible fibrous physical demonstrations will be spe- about being vigilant in observing particles then accumulate in the colon cies specific. These problems, if not their pet and noting any changes in and are rapidly transported to the rec- resolved, can become life threatening. their diet or daily bathroom habits tum for defecation, usually within 4 Chronic constipation causes severe then recording these and letting their hours of ingestion. However, a diet pain, endotoxemia, decreased blood veterinarian know as they make their low in fiber in turn results in low flow and eventual necrosis of the in- way through this process with their amounts of fiber in the colon and testinal tissue that if not medically pet. cecum which reduces the production managed aggressively, may lead to of volatile fatty acids, increases pH, surgery. Diagnostic Algorithm and destroys natural microflora. 1. Assess history, physical exam, A diet high in carbohydrates may and clinical signs result in clostridial overgrowth, while a. Auscultation of the abdomen excessive protein can cause increased b. Rectal exam and palpation ammonia which also results in dys- where appropriate biosis. Obesity, inactivity, spinal c. Perform oral exams on lago- trauma, trichobezoars, dehydration, morphs and rodents as this excess fruit or nuts, in combination could be affecting their die- 4. Urine analysis crease the water content of stool. It is tary intake 5. Abdominal Radiographs most often used in horses for treat- d. Determine from owners if pa- 6. Abdominal ultrasound ment of constipation and fecal impac- tient has ingested any foreign tions via a properly place nasogastric objects tube. Due to the detrimental risk of 2. Rule out iatrogenic disease aspiration, it is administered orally a. Current or past medications via a stomach tube at 10-50 ml per (oral, ophthalmic, otic, topical) dog every 12 hours, 10-25 ml per cat b. Exposure to possible house every 12 hours and 500-1000ml per hold toxins (plants, owner horse up to 2-4 liters daily. Rabbits medications, household may be given 1-2 ml per day for 3-5 cleansers) days. A dose for guinea pigs isn’t 3. Preliminary Lab Results Treatment established. For short term use this is a. CBC There are several options available a certainly an appropriate option but i. Identify a possible for veterinarians to treat constipation for chronic constipation, as soon as underlying infection and GI stasis in their patients, most of laxative use ceases, constipation often b. Chemistry Profile which are focused on the underlying returns. This product is generally safe i. Serum chemistry disease such as giving fluids for dehy- in the hands of a practitioner with profiles may identify a dration or surgically removing an ob- minimal side effects of oily stool and comorbid disease state struction. We want to keep all our abdominal cramping. Despite being such as diabetes or renal animal patients well hydrated and OTC, this should never be recom- disease increase the fiber in their diets and mended for owners to give to their c. Urinalysis decrease the amount of carbohydrates. pets due to the deadly risk of aspira- i. Helpful to rule out a However, several of the most success- tion! possible urinary tract ful therapies for treatments of idio- infection as the source of pathic constipation (i.e., feline Lactulose pain and straining megacolon) have been removed from This is a disaccharide sugar con- 4. Radiographs the US market and are only available taining both fructose and galactose.