Cats must be discharged in a non-cardboard carrier. They cannot be carried or transported loose in the car on the way home.
The small amount of remaining radioactivity in treated cats will gradually disappear over the first 1-2 weeks after being released from radioiodine treatment. Until this is complete, however, these cats will emit very low levels of radiation. Because of this, we also require that these cats be isolated for the first week at home (two weeks if children are living in the home, or if anyone in the home is pregnant). The isolation can be any spare room in the house, but it should be one without heavy human traffic.
Caretakers will need to limit their contact with their cat during this at-home isolation period to no more than 30 minutes daily (10 minutes three times daily). During this contact time, snuggling with the cat is strongly discouraged. Instead, petting the cat at arm’s length is the safest approach. We understand that this is an emotionally difficult requirement for most cat owners – we all want to snuggle with our companions, especially when they’ve been away from home for several days – but our concern is their safety, too.
Much of the residual radioactivity will be eliminated through the cat’s urine and feces. Therefore, we ask that caretakers provide their cat with flushable scoopable litter. We ask that owners use plastic liners in the litter box and flush waste products daily. After changing the litter, hands should be washed thoroughly. The litter cannot be emptied into the garbage with the regular trash as it may set off radiation detectors in the landfill.
Many owners have more than one cat in the home and may inquire about the advisability of allowing another cat or cats in the room where the I 131 treated cat is being confined. In general, this is not a problem as long as: 1) The cat that was not treated with I 131 has his/her feet wiped with a warm water cloth or moistened toilet paper that can be flushed (to remove pieces of litter) each time prior to leaving the confined area, and 2) all excrement (urine or stool) in the litter box in the confined area is treated as if radioactive – i.e., scooped twice daily and flushed – no matter from which cat the excrement came.
If the treated cat requires veterinary care within two weeks of being released, Federal regulations require that the care be performed at a facility with a nuclear medicine ward. They cannot be seen at their regular family veterinarian during this time period. However, if the family veterinarian is able to make a house call to the patient’s home, that is acceptable.
Patients should have a thyroid level checked (at your facility) 4-5 weeks after radioiodine therapy. We ask that you forward the laboratory results to us, and that the lab tests, at a minimum, include a creatinine, T4, and a cTSH. We are happy to work with you in interpreting and monitoring follow-up tests.
There are few adverse effects or risks with radioiodine therapy. Since the iodine is specific in its site of action, there is no hair loss or increase in skin pigmentation, as may be seen with other forms of radiation therapy (cobalt radiation). Some cats seem to experience mild discomfort of the thyroid region (thyroiditis) at the beginning of therapy, but this resolves itself spontaneously and does not cause a problem. A permanent voice change, although rare, is possible.
Occasionally a cat will develop hypothyroidism after treatment with radioiodine. This is easily controlled with supplementation, and more often than not, the supplementation is not permanent. Cats with or without known underlying kidney disease may develop more obvious signs of the kidney disease once the ‘masking’ effects of the hyperthyroidism are removed. Overall, side effects are extremely rare.