Today's Veterinary Practice

JUL-AUG 2014

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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July/August 2014 Today's Veterinary Practice 25 TheraPeuTic uPdaTes in VeTerinary Toxicology | The only at-home emetic agent currently recommended for dogs is hydrogen peroxide; 1 however, note that excessive use of hydrogen peroxide may cause severe hemorrhagic gastritis. Since there are no safe at-home emetic agents for cats, immediate veterinary attention is warranted for eme- sis induction. Veterinary-prescribed emetic agents include apomor- phine hydrochloride for dogs and alpha-2 agonist agents (eg, xylazine hydrochloride, dexmedetomidine) for cats. 1,2 Table 1 provides recommendations for appropriate use of emetic agents. Methods of emesis induction that are no longer recom- mended include digital induction, syrup of ipecac, salt, soap, and mustard powder. Side effects of these methods include oropharyngeal injury, protracted emesis or vomit- ing, hemorrhagic vomiting or diarrhea, lethargy, cardiotox- icity, and hypernatremia. 1,2 INDICATIONS FOR GASTRIC LAVAGE Gastric lavage is indicated for poisoned patients in certain situations, 1,2 but veterinarians rarely perform gastric lavage as it is more labor intensive than induction of emesis. Canine studies have shown that, when gastric lavage was performed within 15 minutes after toxicant ingestion, recovery of the ingested material was poor (38%; range, 2%–69%), and if performed 60 minutes after toxicant inges- tion, only 13% of the ingested material was recovered. 3 Since patients often present more than 1 hour after toxin inges- tion, the clinical usefulness of gastric lavage is questioned. 4 With certain life-threatening toxicants (included in Table 2), however, gastric lavage is highly recommended, espe- Table 1. recommended emetic agents for use in dogs & cats 1,2 EMETIC AGENT MECHANISM OF ACTION DOSE COMpLICATIONS Dogs Hydrogen peroxide local irritation of oropharynx and gastric lining 1–2 mL/kg Po (3% solution) • bloat • hemorrhagic gastritis • gastric ulceration • Protracted emesis • gastric dilatation-volvulus (rare) • Vasovagal response Apomorphine hydrochloride centrally acting, stimulation of the crTZ 0.03–0.04 mg/kg iM, iV or 0.25 mg/kg tablet in subconjuncti- val sac • corneal ulcers • excitement and/or restlessness • ocular irritation (subconjunctival use) • Prolonged emesis • respiratory depression • sedation Cats Xylazine hydrochloride centrally acting, stimulation of the crTZ 0.44 mg/kg iM • bradycardia • Muscle tremors • increased responsiveness • respiratory depression to sharp auditory stimuli • sedation • increased urination Dexmedetomi- dine centrally acting, stimulation of the crTZ 1–2 mcg/kg iV or 40 mcg/kg iM • apnea, bradycardia, sedation • respiratory depression • hyperglycemia • Transient hypertension • hypothermia • Vasoconstriction • Muscle tremors • reduced tear production Table 2. indications & contraindications for use of gastric lavage 1 INDICATIONS • baclofen • cholecalciferol • deadly medications with a narrow safety margin (eg, calcium channel blockers, fluorouracil) • Macrocyclic lactones (eg, ivermectin, moxidec- tin), especially in dogs with abcb1 gene muta- tion • Massive ingestions approaching ld 50 • Materials that can form a bezoar or concretion in the stomach (eg, aspirin pills, prenatal vitamins, bone meal, iron tablets, unbaked bread dough) • organophosphates/carbamates • Patient with clinical signs (eg, decreased gag reflex due to excessive sedation) in which aspi- ration is of concern if emesis is performed CONTRAINDICATIONS • corrosive agent (eg, batteries, drain cleaners, oven cleaners, ultra bleach) • ingestion of sharp objects (eg, sewing needles, knives) • Petroleum distillates or hydrocarbons (eg, gaso- line, kerosene, motor oil), which may be easily aspirated due to their low viscosity • risk for sedation or anesthetic complications • unstable patients (patients in shock and at risk for complications from sedation)

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