Fall 2006

Issue #17

Welcome to the Veterinary Lifeline Partner Program newsletter, brought to you by the ASPCA Animal Poison Control Center.

Contents

What’s On the APCC Website?
Hot Links for the Season
Fall Hazards for Pets
Hotline Humor
Medication Update—Imidazoline Decongestants
Did You Know?
And Did You Know?
Practice Tips
Case Study

What’s On The APCC Website?

The use of rodenticides increases in the fall, as rodents seek shelter from the cooler temperatures and attempt to move indoors. With their increased use, the risk of exposure to pets likewise increases. You can refresh your knowledge of managing rodenticide exposures by downloading and perusing the Toxicology Briefs on anticoagulants (.pdf), bromethalin (.pdf), and cholecalciferol (.pdf). A list of all Toxicology Briefs, encompassing a wide range of toxicants, is available online.

The hazards of xylitol (.pdf), a sugar substitute, to dogs is outlined in our August press release. Xylitol is present in some sugar-free chewing gums, candies, and baked goods.

Clients asking poison-related questions you can’t answer? Point them to the Ask the APCC: Okay or No Way? column on our website. Here they can read answers to questions submitted by others, as well as submit their own questions regarding non-emergent toxicity questions.

Hot Links for the Season

You can access veterinary toxicology information any time of the day or night by going to the Merck Veterinary Manual website.

Adverse drug events (ADEs) are a fact of life, and determining the relative safety and efficacy of drugs requires accurate reporting of such events. You can download a copy of the required FDA 1932 form (.pdf) (pre-addressed and prepaid postage) from the FDA’s Center for Veterinary Medicine website. Alternatively, you may report an ADE to the manufacturer, who is then required to submit the 1932 to the FDA.

Fall Hazards for Pets

Low Toxicity: (may cause gastrointestinal upset, but unlikely to cause serious problems unless very large amounts are ingested)

• Glow jewelry, glow sticks (can cause intense taste reaction)
• School glues, epoxy glues
• Pencils
• Magic markers
• Charcoal briquettes
• Mosquito Dunks containing Bacillus thuringenesis

Moderate toxicity: (may cause significant signs beyond mild gastrointestinal upset)

• Expandable wood glues (e.g. Elmer’s ProBond, Gorilla Glue—even small amounts can form large gastric foreign bodies requiring surgical removal)
• Liquid potpourri
• Batteries
• Charcoal lighter fluid
• DEET

High toxicity: (potential for very serious or life-threatening signs)

• Antifreeze/coolants
• Chocolate
• Rodenticides
• Human medications (cold and flu medications, decongestants)
• Alcoholic beverages
• Homemade “play-dough” (high sodium content)

Hotline Humor

A man called the ASPCA Animal Poison Control Center hotline concerned about his cat. The cat had just been dipped for flea control and was depressed, lethargic and drooling. The hotline veterinarian was concerned that a mixing error had occurred so she asked the owner how he had diluted the dip. The owner stated that he hadn’t mixed up the dip himself. He said that his wife had mixed it up for him because she was the “mathimagician” in the family.

Medication Update: Imidazoline—Decongestants

Imidazoline decongestants are used for temporary relief of nasal congestion from ailments such as colds, hay fever and allergies. They are topical vasoconstrictors in the nose and eyes, but they can also cause adverse effects and can be systemically absorbed. There are a variety of formulations for the most common members of this family—oxymetazoline, xylometazoline, tetrahydrozoline, and naphazoline. The concentration of these products, both nasal and ophthalmic solutions, range from .025% to .1%

These drugs are sympathomimetic agents with their primary effect upon alpha adrenergic receptors. The amount needed to cause clinical effects in dogs is not known, but most dogs will show signs after ingestion of very small quantities. Most commonly signs include vomiting, bradycardia, cardiac arrhythmias, poor capillary refill time, hypo- or hypertension, panting, upper respiratory sounds, depression, weakness, drowsiness, nervousness, hyperactivity and shaking. Typically signs will occur within 30 minutes, but may occasionally be delayed up to 4 hours following exposure.

Treatment is primarily focused on symptomatic care. Decontamination is usually not practical because the product is rapidly absorbed across mucous membranes and the onset of clinical signs is usually rapid. Induction of vomiting and activated charcoal administration are not recommended for patients that are showing signs. Monitoring of heart rate and rhythm (EKG in some cases) and blood pressure are recommended. Electrolyte monitoring (sodium, chloride and potassium) is also recommended. Correct abnormalities as needed. Intravenous fluid administration is recommended to maintain cardiovascular function. Atipamezole (50 mcg/kg, 1/4 dose IV and rest IM) or yohimbine (0.025 mg/kg slow IV, titrate up as needed), both alpha adrenergic antagonists, may be beneficial in cases with significant hypotension; atipamezole has a longer half life than yohimbine, which may decrease the need for repeated dosing. Atropine is sometimes needed at pre-anesthetic doses of 0.01-0.02 mg/kg IV for significant decreases in heart rate. However, continuous heart rate and blood pressure monitoring is required, as there have been some human cases where the use of atropine did not raise the heart rate, but instead raised the blood pressure. Naloxone at 0.04mg/kg IV may be beneficial because imidazolines produce depression, hypotension and bradycardia by stimulation of central alpha adrenoreceptors. Diazepam can be used at .25-.5mg/kg IV for significant apprehension and hyperactivity.

The duration of signs typically ranges from 8 to 24 hours. Prognosis is generally considered good as long as signs are managed appropriately.

Did You Know?

That our website contains a long list of toxic plants that includes the following:

• common name
• scientific name
• family
• toxic principle (if known)
• possible clinical signs
• plant photos

And Did You Know?

That our website also contains a long list of nontoxic plants. Always remember that even with nontoxic plants, ingestion can cause vomiting, diarrhea, or depression. These signs should be mild and self limiting for the most part.

Practice Tips

Activated charcoal is an important tool in preventing and treating toxicosis. Because of the problems that have occasionally been noted with hypernatremia (and subsequent central nervous system signs) in both dogs and cats following activated charcoal administration, careful selection of appropriate patients and situations is indicated. Some important tips when using activated charcoal are as follows:

1. Be sure to weigh out the risks of activated charcoal administration (possible aspiration) if the patient should vomit. Is the benefit that charcoal would provide worth the risk?
2. Take note of the type of charcoal available. Does it contain a cathartic or not? Which is appropriate in the given situation?
3. Use a low dose of activated charcoal (5ml/# or less of Toxiban®) in patients who have vomited on their own or who were induced to vomit.
4. Splitting the dose of activated charcoal and administering half doses at intervals of 1/2 to 1 hour may reduce the risk of the charcoal being vomited up.
5. Give the animal’s digestive tract a bit of time to rest after vomiting before attempting to administer a low dose of activated charcoal (your white lab coat or your technician will thank you!).
6. In depressed patients, always protect their airway to prevent aspiration of charcoal while it is being administered.
7. When giving multiple doses of charcoal, if a cathartic is desired, don’t give it more often than every third dose.
8. Also when giving multiple doses of charcoal, remember that it is usually not given more often than every 4-6 hrs; check serum sodium levels 1-2 hours following administration of repeat doses of charcoal.
9. Hypernatremia secondary to body water shifts into the gut due to the osmotic effect of the charcoal formulations will result in disorientation, muscle fasciculation, tremors and/or seizures. These signs generally occur within 1-3 hours of charcoal administration.
10. Animals showing signs consistent with hypernatremia should be managed with IV fluids (1/2 normal saline or 5% dextrose in water), as well as warm water enemas (50 mL/10 lb).

Case Study—Nuts to You!

A six-year-old spayed female malamute named Angel presented to your clinic with the following signs: moderate weakness, depression, vomiting, ataxia, and some trembling. The owner reported that she had a Labor Day get-together, and about four hours into it, the dog became symptomatic. After starting IV fluids, and giving activated charcoal, you contact the ASPCA Animal Poison Control Center, and reach Dr. Cynthia Gaskill, who is ready to give rapid and expert information.

Dr. Gaskill is told that there was alcohol at the party, but there was no known exposure. Owner reports that there is no way the dog could have been exposed to illicit drugs such as marijuana. Smoking is not allowed in the home, so nicotine intoxication is unlikely. The dog was indoors the entire time, so no possibility of ethylene glycol toxicosis.

While Dr. Gaskill is discussing other possible agents that could cause these signs, such as ivermectin, benzodiazepines, barbiturates, paintballs, xylitol, bromethalin, your technician tells you that the chemistry panel (electrolytes included) and CBC are within normal limits, and the dog just vomited. While going through the vomitus, you find food, activated charcoal, a chewed up ant-bait tray, nuts, pieces of a glow stick, and a dieffenbachia leaf.

1. What does Dr. Gaskill most likely tell you about the vomitus contents?

Initially, what is the safest approach in this case?

a. Signs are not in any way consistent with a reaction to anything in the vomitus.

b. Most ant baits contain a high concentration of avermectin, and this is the most likely cause of these signs. A test dose of physostigmine is routinely used to diagnose avermectin toxicosis.

c. Glow jewelry typically contains n-butyl glycol, which can cause these signs.

d. Dieffenbachia contains soluble oxalates. Hypercalcemia and renal failure is expected to occur within 48 hours.

e. None of the above

The answer is “E,” none of the above.

2. Since there were nuts in the vomitus, you ask the owner what type of nuts were served at the party, and she tells you that she had unshelled pistachios, cashews, English walnuts, almonds, and macadamia nuts. What does Dr. Gaskill tell you regarding this information?

a. According to our database, none of the above species of nuts has ever caused problems in dogs. Signs are classic for marijuana toxicosis, and likely, some of her guests are not being truthful.

b. Large amount of pistachio nuts have caused ataxia in dogs.

c. Signs are consistent with exposure to macadamia nut ingestion.

d. Almonds contain hydrocyanic acid, and dogs are much more sensitive to hydrocyanic acid than people. The dog is lucky to be alive.

e. None of the above.

The answer is “C,” signs are consistent with macadamia nut ingestion.

Between 11/01 and 8/06, the ASPCA Animal Poison Control Center managed 299 cases involving macadamia nuts. The most common signs seen with macadamia nut toxicosis are weakness, depression, vomiting, ataxia, tremors, and hyperthermia. Laboratory changes may include mild elevations in serum triglycerides, serum lipases, and serum ALP, or bloodwork may be normal. Diagnosis of macadamia nut toxicosis is based on a history of exposure and typical clinical signs.

3. What treatment will Dr. Gaskill recommend for Angel?

In this case, one dose of activated charcoal, followed by a warm water enema in 3-4 hours (to enhance the movement of the nuts through the GI tract) may be of benefit. Treatment will include IV fluids, thermoregulation, and supportive care. With macadamia nut intoxication, complete recovery is expected to occur within 24-48 hours.