Illicit Drugs

Chapter 81 Illicit Drugs



Andrew J. Brown, MA, VetMB, MRCVS, DACVEC, Deborah C. Mandell, VMD, DACVECC



KEY POINTS



• Illicit drug intoxication is not uncommon in dogs but is rarely seen in cats.

• Owners rarely volunteer information regarding potential illicit drug exposure but are usually more forthcoming during direct questioning.

• Most intoxications result from ingestion of the drug.

• Unlike other intoxications, animals are usually presented to the veterinarian once clinical signs have become apparent. Urine testing is available for many illicit drugs.

• Amphetamines are indirect-acting sympathomimetic amines, and clinical signs result from enhanced adrenergic stimulation and serotonin syndrome. The hyperdynamic state can result in severe hyperthermia with rhabdomyolysis, neurologic dysfunction, acute renal failure, and metabolic abnormalities.

• Cannabis intoxication results in neurologic and gastrointestinal signs and usually carries a good prognosis.

• Cocaine inhibits presynaptic neuronal uptake of dopamine, norepinephrine, and serotonin, and causes blockade of fast sodium channels. This commonly results in neurologic abnormalities and cardiac arrhythmias.

• Opioid ingestion often leads to sedation, respiratory depression, and bradycardia. Effects can be reversed with naloxone.

• Phencyclidine is a dissociative anesthetic that antagonizes N-methyl-D-aspartate operated calcium channels. Marked central nervous system depression or stimulation may occur.

• Treatment of animals with illicit drug intoxications typically involves emesis, gastrointestinal decontamination, and supportive care. Additional therapies are recommended for specific drug ingestions.


INTRODUCTION


Animals ingesting illicit drugs rarely are presented to the emergency veterinarian before clinical signs have become apparent. Clinical signs will depend on the class of drug, amount ingested, and time from ingestion, but animals typically have sudden-onset altered neurologic activity including abnormal behavior, ataxia, and anxiety. Some animals may vomit secondary to intestinal foreign body obstruction after ingesting whole bags of drugs.


Owners will rarely volunteer a history of illicit drug ingestion although they will occasionally report stories such as the dog “may have gotten into something at the park.” Direct questioning, asking if family members may have illicit drugs, and allowing time for families to discuss this may be helpful. An explanation that illicit drug intoxication, if treated rapidly and correctly, usually carries a good prognosis and will negate the need for an extensive neurologic workup, will typically encourage people to be more forthcoming with information. A urine drug screen using a point-of-care test strip (Medimpex United, Bensalem, PA) or submission to a toxicology laboratory will confirm suspicion.


If a patient presents within 4 hours of illicit drug ingestion, steps should be taken to decrease absorption and hasten elimination of the drug (see Chapter 77, Approach to Poisoning and Drug Overdose). If there is no contraindication to emesis (seizures, depression), then vomiting should be induced immediately with apomorphine or hydrogen peroxide (dogs). Cats are preferably given xylazine for emesis induction. Activated charcoal should then be administered to adsorb any remaining drug. Sodium sulfate (250 mg/kg in dogs and cats) or a 70% sorbitol solution (1 to 2 ml/kg) may be administered as a cathartic. However, within an hour of ingestion, animals are likely to have clinical signs that contraindicate emesis induction. General anesthesia, intubation, and gastric lavage should be considered in these cases.


Dogs that work for police and customs are at an increased risk of illicit drug intoxication. Veterinarians can educate handlers to recognize the clinical signs, induce emesis, and provide supportive care until veterinary assistance can be reached.


Emergency veterinarians should be familiar with the mechanisms of action, clinical signs, antidotes, if available, and necessary supportive care indicated for animals ingesting the commonly abused recreational drugs. Animal intoxications often mirror trends of illicit drug use in humans.



AMPHETAMINES



Pharmacology


Amphetamine (α-methyl-phenethylamine or “speed”) and its active dextro isomer dextroamphetamine, methamphetamine (“ice”), methylenedioxymethamphetamine (MDMA or “ecstasy”), and other derivatives are stimulants used by people with attention deficit disorder, to suppress appetite, to reduce fatigue, and to enhance mood. They are examples of indirect-acting sympathomimetic amines with potent central nervous system (CNS) and cardiovascular stimulatory effects.


Amphetamines are structurally similar to norepinephrine but have only a weak action on adrenergic receptors. They enhance monoamine release from nerve terminals in the brain. Norepinephrine and dopamine are the most important monoamine mediators, with clinical signs that result from postsynaptic adrenergic receptor agonism by these catecholamines. Serotonin is also released from the nerve terminal, which may lead to serotonin syndrome (see Chapter 91, Serotonin Syndrome).



Case Management


Decontamination strategies should be implemented if an animal presents within 30 minutes of amphetamine ingestion (see previous section). Emesis and gastric lavage have little effect after this time, because amphetamines are absorbed rapidly from the gastrointestinal (GI) tract, and clinical signs develop after 30 minutes and last 4 to 6 hours. Activated charcoal should be considered and, with the availability of sustained release amphetamine formulations, repeated doses may be warranted.


Initial clinical signs are similar to those seen with other illicit drugs (i.e., cocaine and methylxanthines) and the effects are dose dependent. These include restlessness, excitability, mydriasis, vomiting, tachycardia, tachypnea, hypertension, and hyperthermia. The owner of an animal manifesting restlessness, excitability, mydriasis, and tachycardia should be questioned carefully as to the possibility of amphetamine exposure. A urine illicit drug screen will confirm suspicion (Color Plate 81-1). Treatment of patients with mild clinical signs is supportive and includes intravenous fluid administration, benzodiazepine therapy to control anxiety and excitability, and careful monitoring of heart rate and rhythm, temperature, and neurologic signs.


With high-dose intoxications, cardiovascular and neurologic effects will result in severe hyperthermia. Clinical signs and their progression are then related to the degree of hyperthermia. The patient will be tachycardic and may exhibit cardiac arrhythmias, seizures, and coma. Consequences of amphetamine-induced hyperthermia have been reported in both dogs and humans and include rhabdomyolysis, disseminated intravascular coagulopathy, acute renal failure, hepatic necrosis, and GI ulceration.1 Treatment should be directed toward aggressive cooling, maintenance of normal cardiovascular function, adequate sedation and cessation of seizure activity with benzodiazepines, IV fluids for potential rhabdomyolysis and renal failure, and prevention of progression to multiorgan failure (see Chapter 167 and 186, Heat Stroke and Anticonvulsants, respectively). Treatment of hypertension with α-blockers, calcium channel antagonists, or nitroprusside may be necessary (see Chapter 178, Antihypertensives). Chlorpromazine and haloperidol may antagonize the effects of amphetamines (and cocaine) by antagonizing or blocking catecholamines.


Urinary acidification to increase the renal elimination of amphetamines has been recommended by some authors. However, this may increase myoglobin precipitation within the tubules and lead to renal failure.


There are reports in the human literature of fatal “water intoxication” in humans that is secondary to MDMA (3,4 methylene-dioxymeth-amphetamine or ecstasy) intoxication.2 A syndrome of inappropriate antidiuretic hormone (SIADH) secretion in combination with excessive water consumption leads to free-water retention, acute hyponatremia, and cerebral edema (see Chapter 54, Sodium Disorders).

Only gold members can continue reading. Log In or Register to continue

Related posts:

  1. Deteriorating Mental Status
  2. Hyperthermia and Fever
  3. Ventilator-Associated Lung Injury
  4. Allergic Airway Disease in Dogs and Cats and Feline Bronchopulmonary Disease

Stay updated, free articles. Join our Telegram channel
Tags:
Sep 10, 2016 | Posted by in SMALL ANIMAL | Comments Off on Illicit Drugs

Full access? Get Clinical Tree
Get Clinical Tree app for offline access