Page 427 - Veterinary Toxicology, Basic and Clinical Principles, 3rd Edition

394 SECTION | IV Drugs of Use and Abuse

Tramadol is a special case, in that it acts as a weak μ
VetBooks.ir receptor agonist but also acts as a serotonin reuptake CNS or respiratory depression. Naloxone can be given
The opioid antagonist Naloxone is used to treat severe
parenterally at a dose of 0.01 0.02 mg/kg and repeated
inhibitor (Indrawirawan and McAlees, 2014).
as necessary since it has a very short half-life. Patients
that fail to respond to a 10 mg dose of Naloxone are
Clinical Signs unlikely to respond to a higher dose.
The clinical effects of opioid drugs are dependent on age Testing of urine or plasma for opioids is available at
(as neonates have an incomplete blood brain barrier), some diagnostic laboratories. Over-the-counter drug tests
species, and the drug involved. Clinical signs in dogs are kits have been used with variable success to detect
similar to those described in humans. Early clinical signs opioids in canine urine (Teitler, 2009).
can include transient excitation and rapid respiration,
drowsiness and ataxia, decreased pain perception, hyper- Other CNS Depressants
salivation, vomiting, defecation, and urination. Dogs
progress to stupor or coma with hypothermia, hypoten- Other drugs may have depressant activities on the CNS.
sion, respiratory depression, and death (Kisseberth and Two commonly used “club drugs” are discussed below:
Trammel, 1990; Dumonceaux, 1995; Branson and Gross, flunitrazepam and GHB. Both are often used by assailants
2001; Volmer, 2005). Other symptoms include decreased to sedate potential victims; thus, there is potential for their
urination and constipation. Symptoms in dogs given low use on guard dogs.
doses of heroin included early aggressive behavior, brief
unconsciousness, weakness, hypersalivation, and respira- Flunitrazepam
tory difficulty, and last up to 8 h (Garrett and Gu ¨rkan,
Flunitrazepam is not sold in the United States but is avail-
1980). Propoxyphene can induce tremors and convulsions
able in more than 60 countries, including many in Europe
in dogs. Cats present with excitation, aggression, insom-
and Latin America, as Rohypnol, Narcozep, and under
nia, and hyperthermia as well as increased pain threshold.
other trade names, as a sedative. Rohypnol has gained
Tramadol overdose in a cat was associated with constipa-
notoriety as the “date rape drug” and is sold as tablets
tion and sedation, but other clinical signs were attributed
imprinted “Roche 1” and “Roche 2,” designating their
to serotonin syndrome (Indrawirawan and McAlees,
manufacturer and milligram dosage. Tablets are crushed
2014). Cats are highly resistant to the emetic effects of
and insufflated or dissolved in a drink intended for an
opioids. Horses, ruminants, and swine also exhibit CNS
unsuspecting victim (Smith et al., 2002; Anonymous,
stimulation. Clinical signs in rabbits depend on the drug
2011). Blue coloring has been added to these pills to
used: morphine induces hypothermia; whereas, apomor-
reduce the potential for this use (Smith et al., 2002;
phine induces hyperthermia.
Rimsza and Moses, 2005). Street names include “roofies”
or “rophies,” “Roche” or “la rocha,” “Mexican valium,”
Treatment “forget me pills,” “Rope,” and “R2.” Injectable forms of
flunitrazepam are also available.
The basis of treatment for opioid exposure is early decon-
Animals that have ingested flunitrazepam should be
tamination, symptomatic and supportive care, and the
monitored closely for respiratory and CNS depression,
judicious use of opioid antagonists. Fentanyl patches have
changes in heart rate, and body temperature fluctuations.
been discovered in the check pouches of monkeys that
If ingestion was recent and CNS depression is not yet evi-
overdosed; thus, checking the oral cavity can be war-
dent, emetics can be given followed by activated charcoal
ranted (Deschamps et al., 2012). Vomiting can be induced
and cathartics to help minimize absorption. Gastric lavage
in animals presenting immediately after ingestion of nar-
can be performed on the intubated patient who has
cotics if they have not already vomited and no contraindi-
ingested a large dose and presents with severe CNS
cations exist. If large doses are ingested and
depression. Analysis is available at some laboratories for
contraindications against emetic use are present, entero-
flunitrazepam, but doses are often quite low and urine
gastric lavage on the intubated animal can be performed
must be collected soon after ingestion.
to evacuate the stomach and instill activated charcoal and
cathartics. Decontamination is likely to be effective for
several hours after ingestion because of decreased gastro- GHB
intestinal motility. Animals must be monitored closely for Another popular “club drug” that has been associated
respiratory depression, the most common cause of death with date rape is GHB. This compound is a derivative
in opioid overdoses. Assisted ventilation is often neces- of GABA and is present in the body under normal con-
sary. Body temperature is maintained and seizures treated ditions. Synthetic GHB can be produced in clandestine
with diazepam. laboratories. It was sold as a nutritional supplement for