Page 414 - Veterinary Toxicology, Basic and Clinical Principles, 3rd Edition

Toxicity of Over-the-Counter Drugs Chapter | 21 381

VetBooks.ir or fleet enemas. Debilitated cats are commonly affected produce black crystals, and though minimally absorbed,
chronic dosing was associated with discoloration of the
(Papich, 1990). Predisposing factors include administra-
kidneys in a rhesus monkey due to accumulation of black
tion of a full-strength fleet enema (intended for human
use) to a small animal, dehydration, preexisting electro- crystals in the renal tubular epithelium (Johnson et al.,
lyte abnormalities, renal or hepatic dysfunction, colonic 2016).
dilatation, and colonic ulceration. A 60 mL hypertonic Kaolin and pectin were previously the active ingredi-
phosphate enema can cause toxicosis in a cat (Roder, ents in the popular OTC product Kaopectate, but bismuth
2004b). Toxicosis has also been reported in alpaca crias subsalicylate is now used. Kaolin is hydrated aluminum
that were inadvertently given sodium phosphate enemas silicate, and acts as an adsorbent. Pectin is a carbohydrate
intravaginally (Bragg et al., 2010). extracted from citrus fruit that acts as an adsorbent and
Sodium and phosphate are absorbed in the colon, and intestinal protectant. Toxicosis attributed to kaolin pectin
absorption is increased with disruption of the mucosa or preparations has not been observed, though these products
in animals with chronic constipation (Jorgensen et al., are likely to decrease absorption of other drugs.
1985). Uptake of phosphate promotes cellular uptake of The OTC drug Imodium, and the prescription drug
calcium, and phosphate can directly bind serum calcium, Lomotil, contain the opioid receptor agonists loperamide
both contributing to hypocalcemia. Adverse effects associ- and diphenoxylate, respectively. Loperamide is sold in
ated with sodium phosphate enemas usually occur within 2 mg capsules and 0.20 mg/mL liquid formulations. The
1 h of dosing. Vomiting and bloody diarrhea have been effective dose for loperamide is 0.08 mL/kg PO every 12 h
observed. Nervous signs that have been reported include in small dogs and cats. These products are poorly absorbed,
depression, ataxia, anxiety, neuromuscular irritability, tre- and function to decrease gastrointestinal secretion and
mors, opisthotonus, and convulsions. Dehydration, weak motility. Side effects include constipation, abdominal pain,
pulses, tachycardia, hypothermia, shock, and death have vomiting, and drowsiness. Collies and other dog breeds
also been observed. Serum chemistry in these patients often with a mutation in the ABCB1 gene are believed to have
reveals hyperphosphatemia, hypernatremia, hypocalcemia, increased susceptibility to loperamide (Sartor et al., 2004).
metabolic acidosis, and hyperglycemia. Hyperkalemia or Clinical signs in collies include salivation, weakness,
hypokalemia can occur. ataxia, and disorientation. Management consists of moni-
Intensive fluid therapy is required in acute sodium toring and supportive and symptomatic care. Activated
phosphate enema overdose situations. The purpose is to charcoal can be given to decrease intestinal absorption in
correct dehydration, electrolyte imbalances, acid base the case of a large ingestion. Neuromuscular signs in one
imbalances, and hypoglycemia and to treat circulatory collie resolved about 1 day after the drug was discontinued
shock. Isotonic saline solution can increase renal calcium (Sartor et al., 2004). The opioid antagonist naloxone can be
loss and, thus, should be avoided. Saline solutions con- used to manage severe clinical signs, but is usually unnec-
taining 0.45% sodium chloride and 2.5% dextrose, or essary. Naloxone has a short half-life, requiring repeated
2.5% 5.0% dextrose solutions, have been recommended dosing as needed (Papich, 1990).
for hypoglycemic patients. Lactated Ringers solution can
be used in hyperglycemic patients. Fluid therapy may be TOPICAL DRUGS
required for up to 4 days. Jorgensen et al. (1985) sug-
gested instillation of aluminum carbonate or aluminum Toxicosis secondary to topical preparations can occur
hydroxide to bind phosphate in the intestine and maintain through dermal absorption or ingestion. Cats, in particu-
body temperature. Prophylactic antibiotics are given for lar, are fastidious groomers, thus any product that is used
compromise of the colonic mucosa. Intoxicated cats on a cat is likely to end up in the cat. Some animals, dogs
showed improvement within 6 h of initiation of therapy, in particular, have been known to chew through tubes
and electrolyte imbalances resolved within 2 days. containing topical drugs (Papich, 1990).
Like other OTC drugs, topical products frequently
contain more than one active ingredient. Antibiotic pre-
Antidiarrheal Drugs
parations can contain bacitracin, neomycin, and poly-
Active ingredients in products used to treat diarrhea myxin. These antimicrobials are poorly absorbed from the
include bismuth subsalicylate, kaolin pectin, and opioid normal gastrointestinal tract, limiting their systemic
receptor agonists. Most of the toxic effects associated effects (Papich, 1990). However, if large quantities are
with bismuth subsalicylate are due to the salicylate com- ingested, damage to the resident gastrointestinal micro-
ponent; therefore, this formulation is discussed in more flora can lead to diarrhea and discomfort. Use of these
detail with aspirin and salicylates. Bismuth is believed to products in hamsters or guinea pigs, which are predis-
adsorb bacterial endotoxin and have a direct antimicrobial posed to develop antibiotic-induced enterocolitis, should
effect. Bismuth does react with hydrogen sulfide to probably be avoided.