Page 406 - Veterinary Toxicology, Basic and Clinical Principles, 3rd Edition

Toxicity of Over-the-Counter Drugs Chapter | 21 373

VetBooks.ir Management early. Treatment consists of observation and supportive
and symptomatic care as needed.
Diagnosis and treatment of salicylate toxicosis is similar
Guaifenesin, or glyceryl guaiacolate, is the most com-
to that described above for NSAIDs. Urine and plasma
testing is available at many veterinary and hospital labo- mon expectorant or mucolytic agent. It is used in veteri-
ratories, but there is a poor correlation between plasma nary medicine as a sedative and muscle relaxant at high
salicylate concentrations and clinical signs (Talcott, parental doses as an adjunct to anesthesia or for seizure
2006). The presence of salicylate in horse urine is controlling. Mild decreases in blood pressure, increases in
expected, even in horses not given aspirin, and is, there- heart rate, and thrombophlebitis are possible side effects
of parental exposures (Plumb, 2015). However, guaifene-
fore, not a significant finding (Boothe, 2001).
sin is present in relatively small concentrations in OTC
Salicylates can inhibit gastric emptying, and gastroin-
products, and oral exposure will most likely cause only
testinal absorption is prolonged with enteric-coated
minimal effects such as vomiting and gastritis. Treatment
tablets; therefore, gastric lavage is sometimes useful up to
for guaifenesin overdose would include early routine
12 h after exposure. Activated charcoal is most useful
detoxification (emesis is likely to be contraindicated), and
within 2 h of aspirin ingestion. Cathartic use does not
symptomatic and supportive care (Papich, 1990).
appear to decrease absorption.
Forced alkaline diuresis is more useful for aspirin than
for other NSAIDs, and is frequently used by physicians. Decongestants
High urinary pH promotes salicylate elimination by trap-
Decongestants can be largely divided into sympathomi-
ping the ionic form in the urine. Alkaline peritoneal dialy-
metic amines such as pseudoephedrine, ephedrine,
sis has been recommended for large overdoses (Davis,
phenylephrine, and phenylpropanolamine (PPA), and
1980; Kore, 1990). Acetazolamide, a carbonic anhydrase
imidazolines such as oxymetazoline, xylometazoline, and
inhibitor, can be used to alkalinize urine, but will exacer-
tetrahydrozoline. Sympathomimetic amines and imidazo-
bate metabolic acidosis. Acid base status must be closely
lines are used as decongestants because of their vasocon-
monitored in any animal undergoing alkaline diuresis.
striction effects.
Monitoring and supportive care for changes in hydration,
electrolyte balance, and body temperature are warranted. Among these, pseudoephedrine is the most common
Clearly, use of NSAIDs to treat hyperthermia must be decongestant associated with toxicosis in small animals,
avoided. Diazepam can be used for seizure management. more often dogs than cats (Papich, 1990). Pseudoephedrine
has been commonly used in cold and allergy preparations,
but due to its illicit use in the manufacture of metham-
phetamine, many US states now regulate its sale.
COLD, COUGH AND ALLERGY Pseudoephedrine is a stereoisomer of the plant alkaloid
MEDICATIONS ephedrine. Ephedrine is found in Ephedra spp. and Sida
cordifolia. Ephedra spp. are used to produce ma huang, an
Medications for the symptomatic relief of cold, flu, and herbal drug used in asthma, allergy, and cold formulations,
allergies are common, and can contain multiple active diet pills, and in various supplements (Means, 1999, 2005;
ingredients, including analgesics, decongestants, antihista- Ooms and Khan, 2001). Phenylephrine is found in nasal
mines, antitussives, and expectorants. Other possible sprays and hemorrhoid creams.
ingredients include ethanol, caffeine, xylitol, and benzo- PPA was commonly available, both OTC and by pre-
caine. These medications can come in a variety of forms, scription, in diet pills, cold and allergy products, and, cur-
including oral tablets, extended-release tablets, dissolving rently, to treat urinary incontinence in dogs (Papich,
granules/tablets, lozenges, and as syrup (liquid). 1990; Means, 2005). FDA issued a public health advisory
Dextromethorphan is a centrally active antitussive. in November 2000 due to increased risk of hemorrhagic
Structurally similar to opioids, it acts on the medullary stroke associated with the use of PPA in humans (Cantu,
cough center and directly suppresses its activity. Due to 2003). Following the advisory, it was voluntarily with-
its dissociative effects at high doses, illicit use of dex- drawn from the market for human use in the United
tromethorphan as a recreational drug has been reported States. Although cardiotoxic effects have been reported in
(Romanelli, 2009). This effect is similar to those of dogs by accidental ingestion (Crandell and Ware, 2005),
ketamine and phencyclidine, which are both controlled PPA is still available as a veterinary prescription drug for
substances discussed in an upcoming chapter. However, the control of urinary incontinence in dogs.
dextromethorphan toxicoses are rare in small animals, Imidazolines are commonly used in OTC eye drops and
sedation being the most common effect, and respiratory nasal sprays. Oxymetazoline is found in nasal sprays as a
suppression is unlikely. If an animal is overdosed with topical decongestant as treatment for allergic rhinitis and
dextromethorphan, activated charcoal can be given epistaxis, as well as in eye drops (marketed as Visine LR).