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When the toxin has been ingested, decontamination involves:

• Induction of emesis within 4–6 h of toxin ingestion (e.g. apomorphine in dogs and xylazine in cats, see Table 4.1), gastric lavage within 2–6 h of toxin ingestion or colonic lavage;

• Administration of activated charcoal with a cathartic (e.g. sodium sulphate or sorbitol; see Table 4.1);

• Providing demulscents (milk, kaolinpectin) for any gastrointestinal irritation.

Emetics that stimulate vomiting by direct irritation of the pharyngeal or gastric mucosa should not be used. Induction of emesis is contraindicated in case of ingestion of caustics or volatile substance, if vomiting has already occurred, and in animals with seizures, impaired mental status or abnormal gag reflex due to the risk of aspiration pneumonia (Rosendale, 2002).

Gastric lavage is performed in the anaesthetized animal by gastric intubation and irrigation of the stomach with warm water. A cuffed endotracheal tube must be in place during the procedure to minimize the risk of aspiration of stomach contents. Gastric lavage is indicated when induction of emesis is contraindicated (e.g. profound CNS depression or seizures) or when a large amount of toxin is likely to still be present in the stomach. Gastric lavage is contraindicated in the case of ingestion of: caustics, small volume of toxin (which can be decontaminated with activated charcoal) and moderate amount of toxin more than 2 h previously. The risks of general anaesthesia and of aspiration pneumonia need to be considered. The animal must be monitored continuously during recovery from general anaesthesia from gastric lavage.

Table 4.1. Medications used in animals with exogenous toxic disorders.

Indication	Medication	Dosage
Seizure control	Diazepam	0.5 to 1.0 mg/kg IV, up to a maximum total dose of 20 mg, or 0.5 to 2.0 mg/kg intrarectally in dogs and cats, repeated to effect or twice within 2 h; if seizures persist, diazepam can be administered as constant rate infusions of 2–5 mg/h in 5% dextrose in water (see Chapter 21)
	Levetiracetam	20–60 mg/kg IV, IM, PO once, followed after 8 h by 20 mg/kg IV, IM, PO q8h (see Chapter 16)
	Phenobarbital	15-20 mg/kg IV, IM or PO divided in multiple doses of 3-5 mg/kg over 24-48 h, and if seizures persist, followed by 2-3mg/kg every 12 h in dogs, and 1.5-2.5 mg/kg every 12 h in cats (see Chapter 13)
	Propofol	1-4 mg/kg IV bolus or 0.1-0.6 mg/kg/min constant rate infusion titrated to effect or up to 6 mg/kg/h (see Chapter 24)
Skeletal muscle relaxation (control of tremors)	Methocarbamol Diazepam	Initial dose 44-220 mg/kg IV given in small boluses of 30-40 mg/kg to effect, up to 330 mg/kg in 24 h in dogs and cats. Oral administration is also an option0.5 to 1.0 mg/kg IV to effect or PO, up to a maximum total dose of 20 mg in dogs and cats, up to three times in 24 h
Induction of emesis	Apomorphine Xylazine	0.04 mg/kg IV or 0.06 mg/kg SC or IM, in dogs 0.4 mg/kg, IM or SC, in cats
Prevention of further absorption of toxin	Activated charcoalSodium sulphate (40% solution)Sorbitol (70% solution)	1-5 g/kg of activated charcoal solution or of powdered activated charcoal mixed with 50 to 200 ml of water to make a slurry250 mg/kg PO once to a maximum of 5 g in cats and 25 g in dogs1 to 2 ml/kg (0.7-1.4 g/kg) PO once
Reduction of free and tissue levels of lipophilic agents	20% lipid preparation for intravenous infusion	1.5 ml/kg IV slow (over 2-15 min) bolus followed by a constant rate infusion of 0.25 ml/kg/min for 30 to 60 min. This may be repeated every 4 h as long as serum is not lipaemic but should be discontinued if a positive response is not seen after three treatments. Animals should be hospitalized and monitored until clinical signs have resolved and the serum is no longer lipaemic as signs of toxicity may return after the intravenous lipid emulsion has been metabolized

Colonic lavage is indicated for toxins than may be absorbed from the colon when ingestion has occurred more than 4–6 h before presentation. Colonic lavage may be beneficial when performed earlier than 4 h post-ingestion of organophosphates and carbamates. Colonic lavage is performed by inserting a lubricated narrow non-rigid tube from the anus into the rectum and transverse colon and instillation of warm water under gravity flow. Animals with decreased consciousness should be endotracheally intubated during the procedure as colonic distension can stimulate emesis.

Activated charcoal can be administered by stomach tube after gastric lavage or syringe-fed to animals that can swallow. Activated charcoal is indicated for adsorption of most toxins when the toxic substance is likely to still be present in the gastrointestinal tract, particularly with toxins with slow gastrointestinal release and adsorption or toxins undergoing enterohepatic recirculation. In these cases repeated dosing of activated charcoal (without sorbitol) 1–4 g/kg PO every 6–8 h for 24 h is indicated. Serum sodium should be closely monitored for patients receiving repeated charcoal doses due to potential of development of hypernatraemia. Constipation can be prevented by maintaining the animal well hydrated. Strong acids or alkalis, dissociable salts and metals, and alcohols are not adsorbed by activated charcoal. Activated charcoal is contraindicated in animals with high risk of aspiration pneumonia or hypernatraemia. Cathartics are often administered in association with activated charcoal to minimize toxin absorption by reducing intestinal transit time. Repeated dosing is not recommended due to the risk of osmotic diarrhoea and hyper-natraemia. Cathartics are contraindicated in dehydrated or hypovolaemic animals.