Monday, March 28, 2011

Radiation Toxicity, Potassium Iodide, and Our Pets

Over the past week I have received a number of questions about radiation both from pet owners and veterinarians about the danger from the nuclear fallout from Japan, not for their human families but also for their dogs and cats.

The question is: should we all be buying potassium iodide for ourselves? Should we also give this to our pets? Since dogs and cats are smaller than we are, could they be impacted by smaller amounts of radiation? What should we do?

The answer to these questions, at least for the time being, is not to take potassium iodide or administer the drug to our pets. So far, the amount of radiation coming here from Japan has been termed negligible by our government. 

What's more, potassium iodide only helps pets (or people) to deal with radioactive particles (I-131) which ultimately impact the thyroid gland, not other organs or illnesses which may result from excessive exposure to radiation.  I understand that we care about our pets and want to be proactive, but we might do more harm than good by giving this iodide supplement.

How does potassium iodine work?
The thyroid gland is the only tissue in the body that wants or needs iodine to perform its normal function (i.e., to make the thyroid hormones T4 and T3, both of which contain iodine in their hormone structure).  As you can see, in the figure on the right, thyroxine or T4 (the main thyroid hormone secreted by the thyroid gland), contains 4 iodine groups on the hormone molecule. T3, the other main thyroid hormone, contains 3 iodine groups on the molecule.

By saturating the thyroid with stable iodide (i.e., non-radioactive iodine), potassium iodide works to block the effects of radioiodine (I-131) on the thyroid gland. In other words, if your thyroid already has all the iodine it needs it will refuse to take up the  I-131.

Of course, there's a catch. Doses of potassium iodide high enough to protect your thyroid from I-131 have some nasty side effects. 

What are the adverse effects of potassium iodide?
Side effects associated with administration of potassium iodide may include gastrointestinal upset, allergic reactions, skin rashes, salivary gland inflammation, hyperthyroidism, or hypothyroidism. That is a pretty impressive list of side effects!

So what should we do?
Since radioactive iodine (I-131) decays rapidly, current estimates indicate there will not be a hazardous level of radiation reaching the United States from this accident. If and when an exposure does warrant the use of potassium iodide, it should be taken as directed by physicians or public health authorities until the risk for significant exposure to radioactive iodine dissipates, but probably for no more than 1 to 2 weeks.

Again, unless the experts declare that radiation levels are high enough, we shouldn't take it or administer it to our pets. If you're determined to purchase potassium iodide for you or your pet, please beware —many legitimate outlets are sold out, particularly if you purchase the potassium iodide online.

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