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Psychotropic medications are posing dangers to pets

Article
Kansas City

Toxic ingestions of human psychiatric drugs can cause clinical signs in pets that range from sympathomimetic to anticholinergic.

psychiatric drugs and pets

Photo credit: Laura/Adobe Stock

This article was updated September 27, 2022.

Many individuals are using medication for their mental health. However, our dogs and cats sometimes get into our pharmaceutical supply and suffer the consequences. In fact, over 30% of calls received by the helpline involve exposures to human medications and supplements, many of them psychotropic, according to Renee D. Schmid, DVM, DABT, DABVT, senior toxicologist at Pet Poison Helpline and SafetyCall International.

Dogs corner the market on pharmaceutical poisonings, at about 65% of cases, she added, while presenting a lecture at the 2022 Fetch dvm360® Conference in Kansas City, Missouri. Although felines claim only one-third of this total, Schmid warned attendees that they are not to be counted out. “Cats really love the taste of these medications,” she said.1

Be it cat or dog, decontamination is rule number one in a toxic situation. For ridding most toxins, however, emesis is only effective within an hour of ingestion.2

Safety should be kept in mind, Schmid noted. “It’s instinctive for us, when an animal has ingested something, to try to get it back out. But when that animal is lateral recumbent, or when it’s bouncing off the walls, it is not a candidate for inducing vomiting,” she said.

Furthermore, consider that each class of psychiatric medication has its very own toxic stamp and specific recommended fix.1

ADHD Drugs

Medications used to treat attention deficit hyperactivity disorder (ADHD) are ubiquitous in American households. According to the CDC, over 60% of children ages 2 to 17 years who are diagnosed with ADHD are using medication to treat it.3

ADHD drugs fall into a few different categories: stimulants, alpha-2 adrenergic agonists, and selective norepinephrine reuptake inhibitors (sNRIs).2

Stimulants

Prescription stimulants are used in children and adults to address ADHD, narcolepsy and, occasionally, obesity. These include amphetamines and methylphenidate preparations.1

Like many psychiatric medications, these generally come in immediate- (IR) and extended-release (ER) versions.2 To ease administration, particularly in children, formulations other than the standard swallowed tablet are available. These include patches, as well as tasty chews, solutions, powders, and beads. The flavorings, which may incorporate xylitol, render them appealing to pets.1

In dogs and cats, amphetamines are generally toxic at 1 mg/kg (0.8 mg/kg for ER formulations). Methylphenidates are toxic at 0.5 mg/kg.1

Clinical signs of stimulant intoxication stem from central nervous system (CNS) excitement and sympathomimetic agonism: agitation, hyperactivity, vocalization, tachycardia, hypertension, head bobbing, tremors, seizures, mydriasis, and hyperthermia.2

A pet that has ingested an IR formulation can experience clinical signs within 20-30 minutes that may persist for 12-24 hours.1 “If the animal is asymptomatic after 3-4 hours, it probably did not actually get into the medications,” said Schmid.

For ER formulations and ingested patches, onset of signs may be delayed by 4-6 hours, and clinical effects can last a day or two.2

The first step in treating these pets is decontamination. If the animal is neurologically appropriate, emesis should be induced. Chewable and oral disintegrating products are absorbed very quickly, leaving little time to induce emesis. If a dog or cat has ingested an IR product and lives far away, the owner should induce vomiting prior to transporting the pet to the hospital.1

For ER products, metabolism is slower, and decontamination can be performed with slightly less urgency. So, if an animal with ER drugs on board lives near the clinic, emesis usually can be delayed until the animal arrives. “Time is on our side,” she said.1

If a patient is neurologically intact, attempts to scavenge any remaining drug can be made by feeding activated charcoal. But once clinical signs have set in, most of the drug has been absorbed, and activated charcoal will not be very effective.1

Schmid also addressed the hazards of drug patches. “Dogs do like to ingest patches,” she said.1

The majority of drug is still active long after patches are discarded. A dog that swallowed one may exhibit significant clinical signs that endure until the patch is completely gone.2

Patch removal can be achieved via endoscopy, or by feeding multiple meals until the patch has been expelled. Activated charcoal can then be used to bind any free-floating drug that has leached from the patch.1

Extended hospitalization is generally required for pets that have ingested patches and other ER products having slow drug absorption.1

Emesis and catharsis should be followed by sedation. “Acepromazine is your friend in just about any toxin case that shows signs of agitation,” Schmid said.1

She recommended a dose of 0.02 mg/kg to 0.04 mg/kg IV, IM, SQ (0.05 mg/kg to 0.1 mg/kg if already manifesting signs). Butorphanol (0.2-0.4 mg/kg IV, IM, SQ), for its cardiac-sparing properties, is safer for some heart disease and geriatric patients. Benzodiazepines should be avoided, as they can cause dysphoria and other CNS effects.1

If a patient is experiencing serotonin syndrome, characterized by CNS, autonomic and neurobehavioral signs like dysphoria, vocalizing and muscle rigidity,2 cyproheptadine (dogs, 1.1 mg/kg; cats 2-4 mg/kg/cat) can be given by mouth or as a slurry per rectum to ease signs. Methocarbamol (55-220mg/kg IV) is useful for animals experiencing tremors, and anticonvulsants like phenobarbital or levetiracetam can address seizures.1

Alpha-2 adrenergic agonists

Guanfacine and clonidine are alpha-2 adrenergic agonists that act centrally to modulate the symptoms of ADHD in children and adults.2 Clonidine is also used for autism, Tourette syndrome and insomnia in people, and to treat behavioral issues like phobias and separation anxiety in dogs.1

These drugs have a narrow margin of safety in pets,2 and clinical signs—which include depression, sedation, ataxia, vomiting, bradycardia, hypotension, tremors and seizures in dogs—can develop in doses as low as 0.01 mg/kg to 0.02 mg/kg. Onset occurs within four hours after ingestion, and effects can persist for 24 to 72 hours.1

Emetics (within 30 minutes of ingestion) and activated charcoal can be administered to asymptomatic patients. If symptomatic, the alpha-2 adrenergic antagonist atipamezole (50 mcg/kg IM, redosed PRN) can be used to reverse signs of poisoning. (Anticonvulsants are indicated in the rare case of seizures.) Intravenous fluids should be given to maintain blood pressure, perfusion, and hydration. Vital signs, particularly heart rate, must be monitored frequently.1

Selective norepinephrine reuptake inhibitors

Atomoxetine, a nonstimulant sNRI used as a second line treatment for ADHD,2 can cause sedation/agitation and anorexia at low doses in dogs and cats; and hypertension, tachycardia, and tremors at higher doses.1

Treatment is with emesis induction for recent ingestion, followed by a single dose of activated charcoal. Further support may include sedation for agitation, antiemetics for nausea/vomiting, beta blockers for persistent tachycardia, methocarbamol for tremors, and intravenous fluids for cardiovascular support.1

Antidepressants

Some 25 million American adults have experienced a major depressive episode in the last few years, according to the CDC. The population most afflicted—at a rate of 21%—are those aged 18-29 years.4

This is important, said Schmid, because “a lot of times, (this age group) may not store medications in their original packaging or may leave medications lying around, increasing the ability of their pets to get to them.”

Selective serotonin reuptake inhibitors (SSRIs)

Used in both people and pets to address anxiety-based behaviors, SSRIs bathe the CNS with “feel-good” seratonin by blocking its reuptake in the presynaptic membrane.2,5 Common SSRIs include fluoxetine, citalopram, escitalopram, paroxetine and sertraline. Trazodone, though not a true SSRI, also blocks serotonin reuptake to produce a calming effect.1

The toxicity profile for SSRIs varies by species, with cats being more sensitive than dogs.2 Small overdoses of 2 to 3 times the therapeutic dose result in sedation or agitation, hypersalivation, vomiting, mydriasis, tremors, and hyperthermia. Larger overdoses can cause ataxia, dysphoria, aggressive behavior, nystagmus, and seizures. Even greater amounts may produce serotonin syndrome.1

Treatment is generally supportive, and involves routine decontamination, intravenous fluids, tranquilizers, methocarbamol, cyproheptadine in the case of seratonin syndrome, benzodiazepines for seizures absent seratonin syndrome, and phenobarbital or levetiracetam for seizures associated with higher ingested doses and/or serotonin syndrome.1

Tricyclic antidepressants (TCAs), etc.

Like SSRIs, TCAs can combat depression and anxiety in both humans and animals.5 Common TCAs include amitriptyline, clomipramine, nortriptyline and doxepin.1

TCAs differ from SSRIs in their narrow margin of safety.2 Overdoses produce anticholinergic effects:constipation, urine retention, mydriasis, hypertension, tachycardia, and disorientation.Vomiting, seizures, and serotonin syndrome may also result.1

Toxicities involving bicyclic antidepressants, like venlafaxine and serotonin and norepinephrine reuptake inhibitors (SNRIs) duloxetine , cause sympathomimetic effects, similar to those seen with SSRI intoxication. Toxicities associated with TCAs, bicyclics and SNRIs are treated similarly to SSRI overdoses; for TCA overdoses, careful cardiovascular monitoring is also advised.1

Benzodiazepines and nonbenzodiazepine sleep aids

Benzodiazepines are effective anxiolytics, anticonvulsants, muscle relaxants and sedatives;5 nonbenzodiazepine hypnotics produce sleep in those whose brains fight it.6 Both operate through the inhibitory neurotransmitter gamma-amino butyric acid (GABA).2,5

Benzodiazepines used in humans and veterinary medicine include alprazolam, diazepam, midazolam, and clonazepam.5 For nonbenzodiazepine hypnotics,5 think zolpidem, eszopiclone, and zaleplon. Of these, clonazepam and zolpidem account for the most Pet Poison Helpline calls.1

With their wide safety margins, benzodiazepines and nonbenzodiazepine poisonings rarely cause fatality in animals.2,6 Clinical signs of acute toxicity, occurring within 30-60 minutes after ingestion, are vomiting, ataxia, disorientation, and either sedation or paradoxical CNS stimulation. In cats, chronic oral use of diazepam can lead to hepatic failure, though acute exposures do not carry the same risk.7

Treatment for these overexposures is much the same as for the other psychotropics: decontamination and supportive care. If paradoxical agitation occurs, sedation can be achieved with acepromazine or butorphanol. In rare cases of severe CNS or respiratory depression, the antidote flumazenil (0.01 mg/kg IV, PRN to effect) can reverse signs.1

The dietary supplement 5-hydroxytryptophan (5-HTP) has become popular for inducing sleep, enhancing mood, and promoting a sense of wellbeing. As an over-the-counter medication, Schmid explained, “Owners think it’s safer and won’t be a problem for pets.”1

Nonetheless, she warned of this serotonin precursor’s narrow margin of safety in dogs and cats: at just 3 mg/kg—a single 100 mg capsule in a medium-sized dog—agitation, tachycardia, hypertension, vomiting, diarrhea, and transient blindness can occur within 2 to 4 hours of consumption. Treatment is by decontamination, intravenous fluids, sedation, cyproheptadine, methocarbamol and cerenia.1

Medications for bipolar disorder

Lithium, lamotrigine, and antipsychotic drugs such as olanzapine, risperidone, aripiprazole and zipsidone are used to treat bipolar disorder in people. Like other drugs, they sometimes end up in canine and feline stomachs.1

Signs of overdose vary with the compound, but generally encompass lethargy, hypotension, heart rhythm disturbances, tremors, and seizures; acute overdoses of lithium are well tolerated, with only lethargy, mild vomiting, and anorexia.2 

Management is by decontamination, supportive care, and medications to address each clinical sign. For lamotrigine overdose, cardiovascular function should be monitored closely, and any ventricular arrhythmias treated.1

Take away

How each case is managed depends on the compound, formulation, ingested amount, and time elapsed following consumption. However, the epidemic of psychological drug toxicities in pets can only be harnessed by client education regarding safe storage.1

References

  1. Schmid R. Common psychiatric pharmaceutical poisonings. Presented at: Fetch dvm360 Conference: August 26-29, 2022; Kansas City, MO.
  2. Hovda L, Brutlag A, Poppenga RH, Peterson K. Blackwell’s Five-Minute Veterinary Consult Clinical Companion: Small Animal Toxicology 2nd edition.
  3. Data and statistics about ADHD. CDC. Reviewed August 9, 2022. Accessed September 26, 2022. https://www.cdc.gov/ncbddd/adhd/data.html.
  4. Symptoms and depression among adults: United States, 2019. CDC. Reviewed September 23, 2020. Accessed September 26, 2022. https://www.cdc.gov/nchs/products/databriefs/db379.htm
  5. Plumb DC. Plumb’s veterinary drug handbook. 9th ed. Ames, IA: Wiley-Blackwell, 2015.
  6. Lancaster AR, Lee JA, Hovda LR, et al. Sleep aid toxicosis in dogs: 317 cases (2004–2010). J Vet Emerg Care. 2011;21:658–665.
  7. Center SA, Elston TH, Rowland PH, et al. Fulminant hepatic failure associated with oral administration of diazepam in 11 cats. J Am Vet Med Assoc. 1996; 209(3):618-625.
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