Page 430 - Veterinary Toxicology, Basic and Clinical Principles, 3rd Edition

Toxicity of Drugs of Abuse Chapter | 22 397

VetBooks.ir and Volmer, 2006; Thomas et al., 2014). Death was with an apparently favorable response to diazepam died
within 72 h according to one study (Catravas et al., 1977).
attributed to hyperthermia, secondary to increased muscu-
lar activity and peripheral vasoconstriction (Catravas and
A clinical study found that two of three dogs had seizures
Waters, 1981; Dumonceaux and Beasley, 1990; that were refractory to benzodiazepines (Thomas et al.,
Dumonceaux, 1995; Frazier et al., 1998; Vroegop et al., 2014). Barbiturates or propofol CRI have been recom-
2009). Frazier et al. (1998) report a body temperature of mended to treat refractory seizures. Chlorpromazine given

105 F (40.56 C) in one dog. Respiratory and cardiac before cocaine dosing was effective experimentally to
arrest, the latter attributed to coronary vasospasm, have reduce severity of seizures, maintain blood pH, maintain
also been implicated as cause of death. body temperature, decrease heart rate and blood pressure,
Hyperglycemia (4/19), increased serum lactate or lac- and prevent arrhythmias (Catravas and Waters, 1981).
tic acidosis (12/19),and hypernatremia (9/19), were Clinically, acepromazine and chlorpromazine have been
reported clinically, with occasional respiratory alkalosis, used to control hyperexcitability refractory to benzodiaze-
hyponatremia, and hypochloremia (Thomas et al., 2014). pine, but multiple doses of acepromazine were sometimes
Queiroz-Neto et al. (2002) report mild clinical signs in required (Thomas et al., 2014). Affected animals with
horses given low IV doses of cocaine: increased alertness, severe, prolonged respiratory depression require respira-
irritability, muscle tremors, vocalization, and stereotypical tory support, including intubation and mechanical ventila-
behaviors like head-bobbing and pawing at the ground. tion. Cardiac symptoms such as tachycardia are usually
Cribbing was reported at higher doses. Most horses defe- short-lived and respond to sedation (Thomas et al., 2014).
cated within 10 min of dosing and recovered within IV fluids with sodium bicarbonate are likely to effectively
20 min. decrease electrocardiogram changes and risk of ventricu-
Lesions reported in dogs include subendocardial and lar arrhythmia development. Treatment of life-threatening
epicardial hemorrhage, degeneration of cardiac myofibers, cardiac arrhythmia with beta-blockers such as propranolol
coronary vasoconstriction, pericardial effusion, and pul- has been recommended, but pretreatment of dogs with
monary hemorrhage. propranolol before cocaine injection did not increase sur-
vival. Beta-blockers are known to produce systemic
hypertension (Vroegop et al., 2009).
Treatment Urine and plasma are routinely tested for cocaine at
Early decontamination of dogs that have recently ingested many laboratories. Thin-layer chromatography and immu-
cocaine has been recommended, but is likely to have lim- noassays are used as a screening method with confirma-
ited effects because the drug is absorbed extremely rapidly tion by GC/MS. Over-the-counter test kits are available to
(Dumonceaux and Beasley, 1990; Dumonceaux, 1995). test for cocaine in urine and have proved useful clinically
Furthermore, emesis is likely to induce seizures (Volmer, (Thomas et al., 2014).
2005; Llera and Volmer, 2006). Sedation and gastric The prognosis is guarded to good with aggressive
lavage in the patient who has ingested a large quantity of medical treatment, and in a clinical study 19/19 dogs sur-
cocaine is a safer method of decontamination. Activated vived with medical treatment, though some neurologic
charcoal and a cathartic can be given orally. Police dogs and cardiovascular symptoms remained after discharge
that have ingested bags of cocaine require cautious endo- (Thomas et al., 2014).
scopic or surgical retrieval to prevent bags from rupturing
or causing obstruction. Surgically implanted bags must be
removed with equal caution and secondary infection treated Amphetamines
as necessary. Because cocaine is highly lipophilic, IV infu-
sion of lipid emulsion is likely to decrease the bioavailabil- The term “amphetamine” refers specifically to α-methyl-
ity and clinical effects of cocaine. phenylethylamine, a Schedule II drug, but the term is
Symptomatic and supportive care includes maintaining often used to describe various derivatives. The term
body temperature, acid base and electrolyte status, and “amphetamines” (plural) is used here to describe a group
monitoring cardiac and respiratory function. Body tem- of related compounds unless specified otherwise.
perature can be maintained by use of a cool environment, Common amphetamines include the Schedule II drug
cool fluids, cool bath, wet towels, fans or cool water ene- methamphetamine and Schedule I drugs 2,5-dimethyoxy-
mas, but avoid inducing shivering, which will increase 4-methylamphetamine (“DOM,” “STP”), 2,5-dimethoxy-
body temperature. Decreased stress also prevents 4-bromoamphetamine (“DOB”), methylphenidate,
hyperthermia. 4-methylaminorex (4MA), and 3,4-methylenedioxy-N-
Seizure control also prevents hyperthermia. Diazepam ethylamphetamine (MDEA). The “designer drug” MDMA
and midazolam have been used to control hyperexcitabil- (“ecstasy”) has some unique characteristics and is
ity and seizure activity; however, two out of six animals discussed separately below.