By Ahna Brutlag, DVM, MS, DABT, DABVT
Director, Veterinary Service & Sr. Veterinary Toxicologist 
&
Kia Benson, DVM
Associate Veterinarian, Clinical Toxicology

d-CON® is one of the most popular brands of rodenticide in the US. It’s so popular, pet owners may unwittingly refer to all rodenticides as “d-CON®”, similar to the way many of us use the word “Kleenex®” when referring to tissues. This generalization can cause problems for veterinary staff when clinicians (and Pet Poison Helpline staff) are trying to determine what type of rodenticide a pet was exposed to. As veterinary professionals, we know that not all rodenticides contain the same active ingredient; however, for the past several decades, we’ve been able to rely upon the fact that all d-CON® rodenticides were anticoagulants (blood thinners). Not anymore. Starting this year, d-CON® is transitioning their residential rodenticides to very different active ingredient—cholecalciferol (vitamin D₃). Since rodenticides are amongst the most common toxins ingested by cats and dogs, it’s imperative that veterinary professionals be aware of this change and understand its medical implications. In addition to the information shared below, Pet Poison Helpline® is hosting a free, RACE approved webinar on August 23, 2018 to teach veterinary professionals how to diagnose and treat cholecalciferol exposure in dogs and cats. For more information, click here. Can’t make the live webinar? No worries. It will be recorded and archived in our library.

Why the change?

The d-CON^® transition from anticoagulants to cholecalciferol began in January. According to RB, the manufacturer of d-CON^®, the transition is in response to 2011 EPA regulations that restricted the residential use of several previously marketed rodenticides. Most notably, the new regulations banned the use of second-generation anticoagulant rodenticides, commonly referred to as ‘long-acting anticoagulants’ (i.e., brodifacoum, bromadiolone, difenacoum, and difethialone). d-CON^® had contained brodifacoum and difethialone. The 2011 regulations stated that the only allowable active ingredients for residential use were first-generation anticoagulants, commonly thought of as ‘short-acting anticoagulants’ (i.e., warfarin, chlorophacinone, diphacinone); bromethalin (a neurotoxicant with no antidote); or cholecalciferol (vitamin D₃). Initially, d-CON^® switched to diphacinone but immediately began research and development efforts to reformulate because the first-generation anticoagulants required multiple days of feeding to produce rodent lethality and genetic resistance in rats and mice were purported. This left d-CON^® with a choice—begin using bromethalin, a neurotoxicant with no antidote, or cholecalciferol. Due to the risk posed to children and pets by use of bromethalin, RB opted for what they deemed as the safer option.

What does this mean for pets and vets?

Once d-CON has fully switched to vitamin D₃ baits, the majority of rodenticides sold for residential use will either contain vitamin D₃ or bromethalin (neurotoxin)—neither of which have a safe, accessible, and inexpensive antidote like the anticoagulants did (vitamin K₁). Because the significant difference between these active ingredients with regard to toxicity, mechanism of action, diagnostic testing, and treatment, veterinary staff must be extra vigilant in determining which product a pet was exposed to. No longer is it safe to simply decontaminate a pet and start them on vitamin K₁.

How do I determine what the active ingredient in a rodenticide is?

By law, the active ingredient (AI) of a rodenticide, and its percent concentration, must be clearly listed on the packaging. If that portion of the package is missing or damaged, the AI can also be identified by the registration number assigned by the regulatory agency. In the U.S.A., this is called the Environmental Protection Agency’s (EPA) Registration number, or “EPA Reg” number. In Canada, it’s the Pest Management Regulatory Agency’s (PMRA) Registration number, also called a “PCP number” or “Registration number”. The number will typically be a series of 1-3 number clusters separated with dashes. For accurate identification, you must have the entire number which can be looked up online. Alternatively, you can contact Pet Poison Helpline® or the rodenticide manufacturer for more assistance.

Many rodenticides have an indicator dye added to them which can alert a parent or pet owner of accidental ingestion by spotting the dye in the feces. Unfortunately, bait color is not a reliable indicator of an AI. Some manufacturers use the same dye for all rodenticide products, regardless of the AI. Others will use different colors for different AIs but this is an internal system and does not translate to products made by other companies. Likewise, product formulation alone is not a reliable indicator of AI. Rodenticides come in blocks, pellets, liquids, and powders, none of which are reliably tied to a particular active ingredient.

Pet Poison Helpline® works hard to keep an updated database of rodenticide products and corresponding bait colors and formulations in effort to aid veterinary professionals in cases of exposure involving a known or unknown brand of rodenticide. If you’re struggling to figure it out, call us for help.

What do d-CON’s vitamin D₃ baits look like?

The new d-CON® cholecalciferol bait does not come as pellets or the hard, solid blocks commonly seen with most other rodenticides. Instead, they are the consistency of firm Play-Doh—called “soft baits”—and are individually covered in shrink wrap (see photo below). The bait is designed to be placed in its accompanying bait station without being unwrapped, as the rodents will just chew through the plastic to get to the bait. Some of the bait stations sold with the product meet EPA’s requirements as being “dog and child resistant”. While this may protect some dogs from exposure, it does not mean that a large, motivated dog can’t chew through it. Also, may rodenticide packages are sold with loose “refill blocks” meant to be put into the bait station once the previous one is eaten. Many pet owners disregard this direction and place unprotected baits where pets can reach them. Finally, the exterior product packing is either cardboard or a plastic bag which dogs can readily chew through to access the refill blocks. PPH has had numerous cases of dogs ingesting refill blocks after chewing into a product bag—sometimes even on the car ride home from the store where the product was just purchased!

What are the signs of vitamin D₃ poisoning?

Vitamin D₃ is an essential vitamin in people, dogs, and cats. This means that we cannot live without it.   Under normal circumstances, vitamin D₃ promotes calcium retention and is necessary for other physiological functions. However, excess cholecalciferol causes high calcium and phosphorous concentrations in the body, potentially leading to acute and severe kidney failure within 2-3 days. Soft tissues/organs in the body may start to calcify (dystrophic mineralization). The damage to the kidneys and other organs may be permanent. Cholecalciferol rodenticides have a narrower margin of safety than most anticoagulant rodenticides and only a small amount is needed to cause poisoning in cats and dogs. Unfortunately, clinical signs of poisoning may not be seen for 1-2 days after exposure. Increased thirst and urination, vomiting, decreased appetite, weakness/lethargy, and an ammonia or urine smell to the breath can all develop. By the time signs of cholecalciferol poisoning appear, significant and potentially permanent damage may have resulted. Cholecalciferol ingestions must be treated very quickly.

How do you treat vitamin D₃ poisoning?

Cases are often challenging to manage as patients can require weeks of treatment or monitoring due to the extremely long terminal half-life of cholecalciferol. Because of this, PPH treats these cases with urgency and recommends immediate gastric decontamination in asymptomatic pets following toxic ingestions. Should the patient become hypercalcemic and hyperphosphatemic, therapeutic options include hospitalization on aggressive IV fluid (normal saline) therapy, frequent monitoring of laboratory values (kidney values, calcium and phosphorus, hydration levels, etc.) to monitor trends, and medications to decrease calcium levels in the blood (including bisphosphonates, diuretics, and steroids). Intralipid (ILE) therapy is not currently recommended.

Want more information?

d-CON® is committed to educating the veterinary profession about cholecalciferol rodenticide exposure in pets. To do so, they’ve asked the experts at Pet Poison Helpline® for assistance. To obtain an in-depth understanding of vitamin D₃ poisoning, view the 1-hour webinar here, sponsored by d-CON®.

For more information on other rodenticides, please click here.