Veterinary Clients Cautioned about Giving Potassium Iodide to Pets

The UC Davis School of Veterinary Medicine has been receiving three to five calls per hour from clients inquiring about potential radiation risks to their pets if radioactive material from Japan’s troubled nuclear power plants should cross the Pacific and reach California.

Dr. Michael Kent, a faculty veterinarian who specializes in radiation cancer therapy, says, “At this point there is no risk to pets in California stemming from radiation released from the tragedy that continues to unfold in Japan.”

“While potassium iodide might help protect dogs, cats and other pets, as it would people, from the risks of radiation exposure in the unlikely event that radioactive iodine reaches here in appreciable levels, giving it ahead of time carries risks and would be ill advised,” Kent said.

In addition, Dr. Kent cautioned, “Side effects to pets taking potassium iodide, especially if they ingest too much, include severe and even life threatening allergic reactions, gastrointestinal upset (vomiting, diarrhea, anorexia), decreased normal thyroid function (hypothyroidism) and damage to the heart. At high enough levels it can cause death.”

Fearing Overseas Radiation, Americans Seek Potassium Iodide for Pets

For more evidence that people love their pets like family, consider the latest reaction in America to Japan’s nuclear crisis:

Especially in western states, agitated pet owners are hitting veterinarians with requests for potassium iodide, a medication that may protect the thyroid gland from cancer caused by exposure to some types of radiation.

Their fear is kindled by radiation leaks from nuclear reactors in Japan damaged by a massive earthquake and tsunami last Friday.

But in the view of veterinary experts in pharmacology, toxicology and oncology interviewed by the VIN News Service, it’s unwarranted.

Besides the fact that significant radioactive fallout is unlikely to occur here from nuclear-reactor leaks in a faraway country, they say, the use of potassium iodide to protect against radiation exposure in dogs and cats is unproven and poses an ethical issue as well.

“People are certainly overreacting,” said Donald Plumb, Pharm.D, author of Plumb’s Veterinary Drug Handbook, the reference book everyone is reaching for to determine what levels of the drug, if any, are appropriate for pets.

“I don’t know that anybody knows what is a reasonable dose of iodine for dogs and cats to prevent damage from ionizing radiation,” said Dr. Sharon Gwaltney-Brant, a toxicology consultant at VIN formerly with the American Society for the Prevention of Cruelty to Animals (ASPCA) Animal Poison Control Center. “The only studies … have been done in humans.”

In the case of a true nuclear emergency and assuming supplies of potassium iodide were adequate to justify distribution to animals as well as people, Plumb said, veterinarians would be left to extrapolate from dosages for children the levels for veterinary patients. However, determining medication levels for pets based on human dosages can be tricky business, Gwaltney-Brant cautioned.

“We know that many times, the doses that work in humans aren’t the same as doses in dogs and cats,” she said. “There may be a difference in how they absorb it (and) how they eliminate it.”

Although potassium iodide is a form of the naturally occurring element iodine, the substance is not benign. In animals, Plumb’s Handbook lists the following adverse effects: excessive tearing, vomiting, anorexia, nasal discharge, muscle twitching, cardiomyopathy, scaly haircoats and dandruff, hyperthermia, decreased milk production and weight gain, coughing, inappetence and diarrhea. It notes that cats are more prone to developing toxicity.

At Veterinary Specialty Center of Indiana, veterinary oncologist Dr. Michael Lucroy determined “There wasn’t anything really I could find out about animal cancers in the area of Chernobyl,” Lucroy said. He noted that giving pets iodine supplements in the absence of a clear need would put them at risk of overdose. “If you’re giving commercial pet food, plenty of iodine is in those diets, anyway,” Lucroy said.

One of the Nation’s Leading Endocrinologists, Theodore Friedman, MD, PhD.  Speaks About the Dangers Associated with Taking Potassium Iodide

Dr. Friedman: “In terms of taking potassium iodide (iodide becomes iodine with oxidation), the iodine can worsen both hyperthyroidism and hypothyroidism. The exacerbation of hyperthyroidism with exogenous iodide has caused a condition known as Jod-Basedow phenomena. This effect is due to the fact that in hyperthyroidism, the gland is hungry for iodine and when you give iodide, you make a mildly hyperthyroid gland much more hyperthyroid as it gets iodine to make much more thyroid hormones. For this reason, iodide can exacerbate mild or potentially cause hyperthyroidism.”

“Iodide also has a detrimental effect in people who could be prone to hypothyroidism. This is called the Wolff-Chaikoff effect. Exogenous iodine can block the synthesis of iodine in patients who are already hypothyroid, and can bring out latent hypothyroidism.”

“Because of the potential detrimental effects that taking iodine can have on the thyroid gland — as well as the infinitesimally low chance that the radioactive fallout from Japan will affect Americans–I strongly recommend against taking iodine supplementation at this time, in response to the Japanese situation. I believe that the risks of potassium iodide outweigh the benefits.”

It’s Not an Armageddon Pill

All potassium iodide (KI) can do is protect the thyroid from one radioactive isotope — radioactive iodine.  It is NOT an “Armageddon pill” or a “radiation protector pill”. KI provides protection only for the thyroid from radioiodines. It has no impact on the uptake by the body of other radioactive materials and provides no protection against external irradiation of any kind. It is not a general radioprotective agent.

In a radiation emergency, the risk of developing thyroid cancer is thought to justify the risk of taking potassium iodide. But if you are not directly in the path of the radioactive plume, potassium iodide will not only not protect you from anything, but it MAY INCREASE your risk of developing thyroid problems. Let’s be clear about this. Potassium iodide can trigger or worsen hypothyroidism and hyperthyroidism, worsen existing thyroid conditions, cause conditions such as the Jod-Basedow phenomena, and the Wolff-Chaikoff effect, and ultimately cause temporary or even permanent thyroid conditions. It can also cause sialadenitis (an inflammation of the salivary gland), gastrointestinal disturbances, allergic reactions and rashes.

In addition, persons with known iodine sensitivity should avoid KI, as should individuals with dermatitis herpetiformis and hypocomplementemic vasculitis, extremely rare conditions associated with an increased risk of iodine hypersensitivity. Thyroidal side effects of stable iodine include iodine-induced thyrotoxicosis, iodide goiter and hypothyroidism. Individuals with multinodular goiter, Graves’ disease, and autoimmune thyroiditis (Hashimoto’s Thyroiditis) should be treated with caution, especially if dosing extends beyond a few days.

Federal and state agencies have been monitoring the situation closely. The U.S. Nuclear Regulatory Commission (NRC) has stated that currently there is no health risk for radiation exposure to people in the U.S. from the events in Japan. The NRC advises that individuals should not use countermeasures (such as potassium iodide) unless advised to by local or federal health authorities.

According to the U.S. Food and Drug Administration, “There is no public health event requiring anyone in the U.S. to take KI because of the ongoing situation in Japan,” the agency states on its website, referring to potassium iodide by its chemical abbreviation KI.

References:

UC Davis School of Veterinary Medicine Press Release

VIN Veterinary Information Network News Service

U.S. Nuclear Regulatory Commission

Guidance Potassium Iodide as a Thyroid Blocking Agent in Radiation Emergencies, U.S. Department of Health and Human Services, Food and Drug Administration, Center for Drug Evaluation and Research (CDER)

FDA Public Health Focus Press Release on Radiation Safety Regarding questions about food safety and medical devices following the nuclear reactor damage in Japan