Pet Owners Guide to Poisons

DRUGS

Animal poisoning by drugs is by far the most common type of small animal poison exposure, accounting for 75% of 1990 toxin exposures as reported by the AAPCC and 82 of 425 fatalities. Dogs and, less frequently, cats, can be poisoned by human or veterinary drugs as a result of accidental ingestion or overdose just like children can; it is worth emphasizing that all medications should be placed out of reach of inquisitive noses which are too often attached to undiscriminating mouths!

This section focuses on those medications which are too frequently given by well-intentioned owners for the purpose of relieving discomfort experienced by the animal and which instead can cause a much more serious problem for the pet. Human over-the-counter pain relievers are occasionally used in veterinary medicine for pain relief but they should only be given upon specific advice and direction of a veterinarian.

Pain relievers, or analgesics, are not designed for use by cats and dogs and a minimal human dose can poison a pet. Cats and dogs do not utilize and tolerate drugs in the same way people do and human drugs should NEVER be assumed to be safe for animals.

ACETAMINOPHEN (TylenolT) - XXX

Tylenol is, of course, the human over-the-counter analgesic medicine used to relieve pain. In people, after the pills are taken, the ingredients are broken down in the body by enzymes in the liver. In people, Tylenol is generally a safe and useful painkiller. Cats, however, have less of the enzyme required to detoxify the drug following ingestion. As a result, there are many dangerous metabolites, or break-down products of acetaminophen that bind to red blood cells and other tissue cells, resulting in the destruction of these cells.

There may also be direct damage to tissue cells from the painkiller. As little as one regular strength tablet (325 mg) can poison a cat to the degree that it can develop noticeable clinical signs of illness. Two extra-strength tablets are likely to kill a cat.

Dogs (particularly small dogs) are also susceptible to significant tissue damage from as little as two regular strength Tylenol and repeated doses increase the risk significantly. Signs develop quickly and can include salivation, vomiting, weakness and abdominal pain.

Due to the significant toxicity to pets in relatively minimal dosages, the recommendation is clear - Tylenol should not be given to dogs or cats. Other, safer, drugs are available for pain relief; talk to your veterinarian about your own pet's specific needs.

ASPIRIN, IBUPROFEN, PHENYLBUTAZONE, NAPROXEN (NSAID toxicity) - X

The pain relievers discussed here are known as NSAID's (non-steroidal anti-inflammatory drugs) and are widely prescribed with caution by veterinarians to relieve pain from arthritis and other conditions.

Animal dosages, however, are much lower than human dosages. Use of NSAID's can significantly increase the risk for development of stomach or intestinal ulcers, particularly in a sick patient, or one receiving other medications.

These pain relievers cause signs of poisoning by decreasing the mucous production in the stomach. Mucous serves to protect the stomach from the acids it secretes and reduction in mucous production decreases the protection the stomach has from acid secretion and increases the likelihood of ulcer formation.

In addition, these drugs indirectly decrease the blood flow to vital organs, particularly the kidney, and can result in significant kidney damage. Two regular strength aspirin in a small dog can cause clinical signs of poisoning. As with Tylenol, cats are more sensitive to these drugs and should never be given these medications unless under the specific direction of a veterinarian.

Again, these drugs can be safely used and, in fact, are employed in veterinary practice every day in appropriate doses and after careful medical evaluation of the patient. The important point is to recognize that dogs and cats do not respond in the same way to human medications that people do. Any medications need to be discussed with and prescribed by a veterinarian prior to giving them to your pet to avoid an inadvertent and tragic poisoning.

HOUSEHOLD PRODUCTS

The category of "household products" probably contains most of the non-drug substances that poison animals throughout the country each year. This would include insecticides designed to kill ants, fleas, termites, wasps, etc., pesticides against rats, mice, gophers and other unwanted pests, herbicides to kill weeds in our yards and gardens, cleaners for our homes and businesses, and ethylene glycol and fuel and other petroleum products used in cars, heaters, and even lighters. These are products which are both widespread in use and frequently highly toxic.

The combination of being common and deadly frequently results in a very dangerous situation for household pets who share our homes, cabins, yards and cars.

For ease of reading and organizational purposes, I have split this category into five narrower groupings. Remember, however, it is the toxic active ingredient in the substance the pet is exposed to which will determine how much danger is present. Therefore, it is critical in any case of potential poisoning to find the container of the toxic substance and know the ingredients when seeking advice or veterinary services. All rat poisons are not alike and the same is true of ant poisons, herbicides, flea products, etc.

Different poisons may require very different treatments and it is necessary to know the active ingredient in a potential poison to know how to treat an exposed animal and to give a reasonably accurate prognosis. Ideally, the veterinarian should have the intact container with the label when evaluating the toxic potential of the product.

ANT POISONS/MISCELLANEOUS INSECTICIDES - XX

There are dozens of insecticides available in hardware and home repair stores designed to kill ants, termites, wasps, garden pests and many other nuisance insects. Unfortunately, these products present a risk to our household pets when a dog or cat is accidentally exposed to the poison, usually by eating the bait or poison. Although there are a host of different active ingredients found in these preparations, many of them can be grouped into two categories: Organophosphates and carbamates.

Both organophosphates (known as OP's) and carbamates have similar toxic effects which involve disruption of the normal nervous system function by causing an excess of the neurotransmitter, acetylcholine, to accumulate in the body. Although acetylcholine is a necessary body chemical for normal nervous and muscular function, this excess or overdose, causes severe clinical signs that can result in the death of the animal. If an animal is exposed by eating a poison containing OP's or carbamates (or, less frequently, absorbing the substance through the skin in a dip product) it can experience a number of clinical signs. These include excess saliva production, lacrimation or tearing of the eyes, excessive urination, diarrhea, muscle twitching, weakness, difficult breathing and collapse. It is critical than an animal potentially exposed to these insecticides be evaluated by veterinary personnel as quickly as possible in order to provide treatment if necessary before signs become severe, at which point treatment is often ineffective.

There are many other types of insecticides besides OP's and carbamates, including: Chlorinated hydrocarbon compounds, pyrethrins, arsenic and others which have different poisonous properties and which may require different treatments for accidental exposure. As mentioned earlier, in the case of an accident, it is important to get the container with the label including the insecticide's active ingredient(s) and bring that information to the attention of the veterinary staff. They can then determine the type of toxicity and any possible treatments as quickly as possible, preferably before the pet is very sick. Many of these products are extremely toxic and any delay in evaluation of the cat or dog can be life-threatening.

ANTIFREEZE - XXX

Poisoning by antifreeze, or ethylene glycol, is one of the most common small animal toxicities, particularly up here in the cold north. Every year do-it-yourself motorists get out the gear needed to winterize their vehicles, including antifreeze.

Unfortunately, this poison has a sweet taste and spilled or leaked antifreeze is lapped up by many dogs and cats in quantities sufficient to cause severe sickness and even death.
It takes only about 1/2 teaspoon per pound for a dog to get a toxic dose of ethylene glycol, the active ingredient in antifreeze, and less for a cat. Although the poison affects both the animal's neurological and kidney function, the most severe damage usually involves the kidneys. Clinical signs in affected animals include depression, incoordination, vomiting, and seizures.

The best way to combat antifreeze poisoning is by preventing the animal from having the opportunity to drink the poison. Keep all containers tightly closed when not in use and clean up spills immediately. It should be noted that this toxin affects people as well as pets and that small children are also at risk for ethylene glycol poisoning.

There is currently a new product on the market (one trade name is SierraT) which claims to be safer than other brands of antifreeze. This product contains propylene glycol as its active ingredient. If ingested, it can still cause the nervous system injury resulting in incoordination and possibly seizures but does not cause the more frequently fatal kidney damage. It is clear using such a product would pose less of a health hazard. The best advice remains, however, to always use any potentially toxic product carefully to prevent accidental poisoning in the first place.

CLEANING PRODUCTS - XXX

Again, this category contains dozens of products used around the home including toilet bowl cleaners, bleach, detergents, caustics (e.g., DranoT, AjaxT), pine oils and others. Although intended to keep our lives safe and healthy by maintaining a clean environment, these products are often highly poisonous to living tissue if a dog or cat eats or becomes otherwise exposed to the chemicals in the cleaner.

These cleaners can destroy tissue on contact by acid or alkaline burns, by dissolving through tissue membranes, by absorbing through to the animal's bloodstream and causing generalized illness and a variety of other mechanisms. Pine oils and electric dishwashing detergents particularly tend to be quite toxic although the range of chemicals included in cleaning products can cause signs varying widely from mild local irritation (many detergent soaps) to deep penetrating tissue damage (alkaline products) to severe systemic disease (pine oils and others).

Once again the best remedy is prevention. Keep all cleaners tightly closed when not in use to prevent accidental spills and ingestion. Also, be sure to keep pets out of newly cleaned areas to avoid paw injuries from walking in the newly applied cleaning solution and mouth burns from the animal then grooming itself. Also be aware of the possible dangers of toilet bowl cleaners from dogs and cats who consider the toilet just another water bowl!

In case of accidental exposure to cleaning products, it is generally recommended to flush the skin (or mouth) with plain water to wash away remaining chemicals, then call in to your veterinary clinic for further instructions. In the AAPCC 1990 report, 5.9% (2,217 animals) of all non-drug poison exposures were inquiries following exposure to cleaning products, with 80 of those animals being moderately to severely affected.

FLEA PRODUCTS - X

Millions of dollars are spent every year on products designed to rid our non-human companions (and our homes!) of these unwanted pests. Fleas are highly irritating to dogs and cats and can sometimes result in severe flea bite allergies for those animals who develop a sensitivity to proteins in the flea's saliva. Most of the products on the market to combat these insects (the most common of which is Ctenocephalides felis, the cat flea) create few problems when used as directed.

Unfortunately, some dog flea preparations can be toxic to cats and almost all topical flea preparations (dips, sprays, etc.) can be poisonous if not used in accordance with label instructions. If label instructions are for once weekly use, and the product is used daily or more often, poisoning can result. If premise sprays, specifically not for use directly on pets, are used on or near pets, poisoning may result. The message is clear - use brand names you are familiar with (ask your vet for recommendations if you're not familiar with any specific products), and use according to label instructions. STOP use if your animal shows any abnormal signs (possibly poor appetite, depression, vomiting, diarrhea, excessive salivation).

Excessive drooling may be caused only by the taste of the product, or may truly be of concern. Contact your veterinary clinic. Consider bathing your pet in warm water with diluted liquid dish detergent to remove flea products from the hair and skin oils, thereby limiting your pet's exposure.

Every year hundreds of animals are poisoned by these products, some fatally, by accidental misuse resulting from misreading, or failing to read, the label instructions. Do not use products intended for dogs on cats as these may contain compounds that are appropriate for dogs but poisonous to cats. Do not use premise sprays intended for the house and/or yard on or near pets and always carefully read instructions prior to use. Call your veterinary clinic with any questions or if your animal shows any clinical signs during or following flea treatment.

HEAVY METALS (Lead, Zinc) - X

Lead poisoning is seen occasionally in small animals, notably in birds, frequently as a result of ingestion of a foreign object containing lead, for instance, a toy, drapery weight, fishing weight, lead shot or battery. However, it can also be seen with ingestion of lead-containing paint, caulking, motor oil and other lead sources. Clinical signs for animal suffering lead poisoning usually include a combination of signs involving the gastrointestinal system (vomiting, constipation diarrhea, painful abdomen) and the neurological system (depression, blindness, circling, muscle tremors, incoordination). Onset of signs is usually relatively quick but signs can progress more slowly if the animal is slowly being exposed to the poison, i.e., repeated ingestion of lead based paint.

Zinc poisoning occurs most frequently when dogs ingest zinc in the form of pennies. The metal interacts with components of the animal's red blood cells and can cause, weakness, trembling, loss of appetite. Although not seen frequently, it is interesting to note how such a mundane object can be toxic when ingested.

RODENTICIDES - XXX

Poisons intended to kill rats, mice, gophers, moles and other mammalian pests are among the most common and deadly of small animal toxins. Since rodent and other pests and our companion animal dogs and cats are all mammals, it follows that substances highly poisonous to the pests would be just as lethal to our pets, and indeed that is the case.

In the 1990 AAPCC report, 8% of all non-drug toxin exposures resulted from rodenticides and of 425 fatalities, 60 (14%) of deaths were subsequent to these poisons. Commonly, owners have all but forgotten the old rat poison in the garage cabinet until it gets knocked onto the ground and the dog has eaten it. Or on farms or stables, rat poison is left in what seems like a safe place to attract only the rats and then the empty chewed container is seen outside the doghouse. It cannot be too highly stressed that rodenticides are highly toxic and any such poisons designed to kill small mammals need to be carefully contained in closed metal cabinets or high on stable shelving. The poisons usually come in flimsy cardboard containers and any dog, puppy or cat can chew through the container to get at the bait. Unfortunately, every year far too many do just that.
Rodenticides are classified according to both their basic ingredient compounds and by how they act on their target. These categories include: Anti-coagulant rodenticides, cholecalciferol, strychnine, zinc phosphide, bromethalin, compound 1080 and more. The most common rodenticide poisoning seen in veterinary practice is that of the anti-coagulant rodenticides. These poisons - with ingredient names like warfarin, fumarin, diphacinone, bromadiolone - act by interfering with the animal's ability to utilize Vitamin K. One of they key roles of Vitamin K is in the production of coagulation factors in the body which cause blood to clot when necessary.

Although we are not aware of it, normal physiological processes require blood to clot many times a day in our bodies and that of our pets. Without the necessary coagulation factors, normal minor bleeding in the body goes unchecked which, without treatment, becomes major bleeding, with blood loss anemia, hemorrhage and death resulting. With most anti-coagulant rodenticides, signs are not seen until 3-5 days after the pet has ingested the poison. Clinical signs include weakness, difficult breathing, pale mucous membranes, and bleeding from the nose.

Other types of rodenticides have different mechanisms of action with some (i.e., strychnine and bromethalin) causing neurological signs such as incoordination, seizures and others cardiac failure (i.e., cholecalciferol). If accidental ingestion of rat poison is suspected, contact your veterinary clinic immediately, even if your dog or cat is showing no obvious signs of being ill. Be sure, if possible, to bring the poison container in to the clinic in order to determine the specific toxin and provide the best treatment. Early recognition is critical as some poisons, particularly the anti-coagulant rodenticides, can be successfully treated if the poisoning is caught early and treated appropriately.

MISCELLANEOUS POISONS

GARBAGE/FOOD POISONING - X

This is primarily a problem of dogs and cats that roam freely around the farm or neighborhood with easy access to "road kill," garbage cans, etc. However, any animal that eats decaying, rotten carcasses or other food material (i.e., left-over hamburger) that has been contaminated by bacteria and bacteria-produced toxins is susceptible to this poisoning. The toxicity of the rotten food lies largely in toxins produced by bacteria in the food material which are then delivered in the meal to the dog or cat and cause severe gastrointestinal upset.

Clinical signs can include vomiting, diarrhea (which may be bloody), fever, abdominal pain, and weakness. Severely affected animals can go into shock and even die as a result of the absorbed bacterial toxins.

For those animals who are not restricted in their activity it is impossible to prevent possible garbage poisoning (as well as the all too common "hit-by-car" injuries which are a much more common and deadly risk for free-roaming animals). However, if your animal has "escaped" and you suspect he or she has gotten into something very unappetizing (frequently the odor of the meal is obvious even before the pet throws it up!) be aware that this type of poisoning can be quite serious and follow up with your veterinarian if you see any signs of illness (repeated vomiting, lethargy, depression).

TEFLON - X

Teflon toxicity occurs most often in pet birds and in the 1990 AAPCC report on small animal poisoning, resulted in 5 of 425 fatalities. The problem arises when pots or pans containing either TeflonT or SilverstoneT are left on a hot stove until heated to >280 degrees Celsius (generally when a pan is forgotten on a hot stove for some time until it is "white hot"). The result is the release of toxic particles into the air that cause severe damage to the bird's lungs when inhaled. Birds are unable to clear the toxic particles by exhaling, coughing, etc. and are therefore more susceptible to this type of poisoning.

Although hard to avoid as it results from an accident, it might be a good idea to house pet birds a distance from the kitchen (especially if you tend to be an absent-minded cook!)

CHOCOLATE (Drug class: Methylxanthines) - X

It often surprises pet owners to discover that for animals, chocolate is poisonous in sufficient dosages. Specifically it is the drugs in chocolate, theobromine and caffeine (of the drug class methylxanthines), that are toxic to pets. Only a moderate amount needs to be eaten by an animal, typically a dog, in order to be poisonous (approx. 1/2 oz. of baking chocolate per pound of body weight and less in some animals). With the poison in this case being so appealing, overdose is not a rare occurrence. Poisonings of this type typically occur during the holiday seasons of Easter, Christmas and Halloween. Depending on their appetite and the specific ingredients contained in the recipe, some dogs have ingested a toxic dose of chocolate by eating an entire pan of brownies or another chocolate dessert, particularly one containing baking chocolate.

Fortunately, the animal frequently vomits soon after which reduces the amount of poison in the stomach available to act on the body and decreases the toxicity somewhat. If clinical signs are seen, these can include vomiting, excessive urination, hyperactivity, fast breathing, weakness and seizures. While rare, death can occur, usually due to the adverse action of methylxanthines on the heart.

Many people unknowingly feed their dogs chocolate treats (candy bars, cookies, etc.) without obvious illness resulting; the lack of clinical signs is due only to the relatively low dose of methylxanthines in small amounts of milk chocolate. It is certainly better for your pet to stick to treats he or she will like just as much (freeze-dried liver pieces come to mind - yummy!) and avoid chocolate-containing treats where the dog is concerned. Also be aware that an accidental overdose of cake, bars, etc. containing chocolate can pose a significant risk to a dog. If this should happen to your pet, make note of the amount of chocolate used in the recipe, the approximate amount eaten by your pet and give your veterinarian a call to determine if the dose was sufficient to cause any problems.

ACKNOWLEDGEMENT

This guide was generously prepared by Julie Dahlke, DVM, a graduate of the University of Minnesota, College of Veterinary Medicine. She compiled information on poisons which are commonly accessible to pets and which cause their owners great concern. This is not an exhaustive guide to companion animal poisons but instead a useful, readable reference designed for the pet owner. Dr. Dahlke thanks Dr. Mike Murphy, a veterinary toxicologist and Ms. Lynn Lawrence, both of the University of Minnesota for their assistance in the development of this guide.