REPOST: Dr. Ain & Dr. Re: Allergic to Iodine?

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(Dr. Ain)

Date: Thu, 28 Oct 1999 08:17:18 -0400

Subject: Re: Allergic to Iodine?

In-reply-to: <003901bf20cc$1f8fd3c0$abd2afcf@default>

>--

>

> >I am allergic to Iodine. I had a severe reaction to IVP dye.

>

>I'd check into your history carefully to see if it was in fact the iodine that

caused the allergic reaction, as opposed to something else in the mix. I have

read of people who went for years thinking iodine was the culprit when actually

it was one of the inactive additives. RAI is an important part of thyca

treatment in most cases, so you want to have it if possible. Surely, they can

do some sort of test. This is a question to pose to your current docs.

Dear ThyCa Members:

It is not uncommon for people to be allergic to the high quantities of

iodine found in radiographic contrast dye and sometimes in seafood. On the

other hand, the physical quantities of iodine in the radioactive I-131 used for

thyroid cancer scans or treatments are exceedingly small, although quite

radioactive. For this reason, people with known iodine allergies do not

typically have a problem with allergies to radioactive iodine. In fact, despite

having treated many patients with known " iodine allergies " with radioactive

iodine, I have never personally seen (or heard of) any patient having an

allergic response to the radioactive iodine.

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B. Ain, M.D.

Associate Professor of Internal Medicine

Director, Thyroid Nodule & Oncology Clinical Service

Director, Thyroid Cancer Research Laboratory

Division of Endocrinology and Molecular Medicine

Department of Internal Medicine, Room MN520

University of Kentucky Medical Center

800 Rose Street, Lexington, Kentucky 40536-0084

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(Dr. )

Date: Sun, 20 Feb 2000 13:58:13 -0500

Subject: Re: FOR THE DOCTORS - THANKS

Jane wrote:

> FOR THE DOCTORS - THANKS IN ADVANCE

>

> (1) Iodine is an atomic element, it is not a molecule with antigenic

> epitopes. Moreover, it is in almost everything we consume. Therefore, how

> can anyone be allergic to it?

People are allergic to iodine when it is bound to a carrier molecule, like

iodinated contrast used for CT scanning.

>

>

> (1.1) If iodine does not induce a hypersensitivity type immune response,

> then why are benadryl and cortisone sometimes used during I-131 treatment?

In my opinion there is no routine indication for the use of antihistamines (like

benadryl) and steroids (like cortisone or prednisone) in radioiodine therapy,

even in people with known allergies to shellfish or iodinated contrast. There is

more dietary iodine in a low iodine meal than there is in a single 100 mCi dose

of I-131. An allergy to iodine at such low levels would be incompatible with

life. When the rare patient does have an allergic reaction to radioiodine

therapy (I have had only one patient in over 15 years), it is almost certainly

related to a preservative or contaminant in the dose, not the radioiodine

itself. That one patient is the only patient I have ever needed to pretreat with

steriods and antihistamines.

One use of steriods before radioiodine therapy is in the treatment of patients

with brain metastases. The steriods are given to prevent life-threatening

complications of brain swelling, not to prevent an allergy.

> (1.3) Can the use of benadryl and cortisone have negative effects on the

> uptake/function of I-131 during RAI? Isn't the cell death (necrosis with

> inflammatory response) somewhat compromised or slowed?

>

One could make a theoretical argument. There is no known answer in the treatment

of thyroid cancer.

>

> (2) What is the cut-off external measurement of radioactive dose rate (in

> milliRoentgens/hour) at which a patient receiving high-dose I-131 treatment

> may be released from the hospital where you practice?

For my practice the number depends on realistic evaluation of the home

situation.

> (3) Is it yet understood (at the cellular/molecular level) why some patients

> suffering through a hypothyroid period experience affective disturbances?

> Is this a frequent occurrence in such patients? Do you have patients who do

> not experience any significant emotional changes whatsoever during induced

> hypothyroidism?

About 10% of patients have a profound emotional and physical response to

hypothyroidism. About 10% don't even notice. The other 80% feel lousy and are

happy to get back on thyroid hormone, but don't dread the next time they will

have to become hypothyroid.

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A. , MD

Nuclear Medicine, A-72

Albany Medical Center

Albany, NY 12208

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