Page 954 - Veterinary Toxicology, Basic and Clinical Principles, 3rd Edition

906 SECTION | XIV Poisonous Plants

VetBooks.ir decontamination is based on plant toxicity, symptoms, porous final product. Due to its small particle size and
enormous surface area, it can adsorb a large amount of
and time since ingestion. Unless contraindicated, emesis
toxicant. Some “superactivated” charcoal preparations
is preferred to lavage because plant pieces are difficult to
2
remove by gastric tube in some animal species, in particu- have a surface area of up to 3500 m /g or about
2
lar those that are small. 175,000 m per 50-g bottle. This allows the adsorption of
toxins through weak intermolecular forces, with nonio-
nized, organic compounds binding more avidly than dis-
Gastric Decontamination sociated, inorganic ones (Olson, 2010). The usual dose is
Many methods have been used to prevent the absorption 1 g/kg BW or 10 parts of activated charcoal for every one
of toxic substances from the gastrointestinal tract, with part of toxin, whichever is greater (large animals:
varying success. 250 250 g; small animals: 5 50 g). Activated charcoal
Vomiting can be induced in the conscious patient by is effective in preventing absorption of toxicant when it is
the administration of apomorphine, (0.04 mg/kg BW properly utilized. Most toxicologists recommend single-
intravenously (i.v.), or 0.08 mg/kg BW intramuscularly dose activated charcoal at 1 h following a significant
(i.m.) or subcutaneously (s.c.). Apomorphine, a morphine ingestion. Charcoal as a “universal antidote” has a wide
derivative, may cause respiratory and CNS depression spectrum of activity and when properly used is probably
and may induce protracted emesis, ultimately resulting in the most valuable single agent known (Juurlink, 2015). It
a severely debilitated animal. These effects can be con- can be administered after vomiting has occurred or can be
trolled by using a narcotic antagonist such as naloxone used in the gastric lavage solution. Decontamination with
(0.04 mg/kg BW i.v.). When naloxone hydrochloride is a single-dose of activated charcoal is conceptually differ-
given i.v., the dosage may be repeated at 2- to 3-min ent from the use of multiple-dose activated charcoal, a
intervals as necessary (Bright et al., 2011). less commonly deployed intervention involving the
Gastric lavage may be used to enhance removal of administration of multiple (typically, two to six) doses
toxins still present in the stomach. There are two decon- (Juurlink, 2015). The single-dose activated charcoal can
tamination procedures-gastric lavage or irrigation. When be associated not only with altered toxicokinetics (influ-
it is ascertained that an animal has ingested a potentially ence the area under the curve of toxic concentration ver-
poisonous substance within less than 2 h, efforts should sus time, enhancing the total body clearance, and
be made to remove it from the upper gastrointestinal tract. reducing systemic absorption) when given shortly after
If the animal has not vomited and can swallow, an emetic dosing, but also with improvements in clinical outcomes.
should be given promptly. In the case of an irritating The “universal antidote” should be avoided because mag-
toxin, rinsing of the mouth with sodium gluconate for at nesium oxide and tannic acid interfere with the adsorption
least 2 h can be performed. capacity of activated charcoal. Activated charcoal adsorbs
Gastric lavage is an important emergency procedure, most alkaloids well and should be administered in almost
but it is relatively ineffective in suspected poisoning cases all symptomatic cases. Although generally safe, the
in which significant time has elapsed. Changes in techni- single-dose activated charcoal is not free of risk. The
ques (e.g., using a larger tube, more volume, and more most widely cited concern associated with the single-dose
frequent lavages) have proven to be a useful procedure activated charcoal is pulmonary aspiration, although the
when undertaken within 2 h of ingestion of a toxicant risk of this complication is low. GI complications repre-
(Hanna, 1986). Gastric lavage is recommended if the ani- sent another potential risk of single-dose activated char-
mal is presented within 60 min of a potentially lethal coal administration such as bowel obstruction, bezoars,
ingestion of a plant. Proper placement of the patient may and stercoliths.
help prevent aspiration and improve the yield of the pro- Other adsorbents, such as magnesium oxide and kao-
cedure. If more than 2 h has passed since ingestion of the lin, are less effective than activated charcoal. Soap and
plant material, it is likely that the stomach will have water are often used dermally to remove a toxin from the
already emptied into the intestine. In such cases, subject- skin and/or reduce toxin absorption.
ing the pet to further stress through induced emesis is Ipecac syrup and cathartics have not been shown to be
unwise. The patient should be sedate and as large a gas- of benefit in cases of ingestion of poisonous plants.
tric tube as possible should be inserted to facilitate aspira- However, the use of emetics such as syrup of ipecac is
tion of the ingesta back out through the tube. recommended if the animal is conscious (i.e., the poison-
The use of activated charcoal has revolutionized the ous plant does not cause rapid onset of coma and convul-
treatment of poisoning. Charcoal for medicinal use is sions) and the absorption time is less than 2 h.
created by the controlled pyrolytic decomposition of Apomorphine can be injected subcutaneously at a dose of
carbon-based compounds. Activation with gases at high 0.2 mg/kg, but it is effective only in dogs. Ipecac syrup
temperature removes previously absorbed substances and up to 10% at a dose of 1 or 2 mL/kg BW can be used in
further reduces particle size, resulting in an exceptionally cats and dogs. Xylazine is also an effective emetic,