The thyroid is a hormonal gland which is found in the neck underneath the larynge (adam’s apple) and in front of the air tube. The thyroid’s main function is the storage of iodine and the production of thyroid hormones containing iodine. It plays an important role for the catabolism as well as for the growth of individual cells and the entire organism. Thyroid hormones e.g. control basic life functions such as heart beat, body temperature and digestion. Thyroid illnesses may lead to disruptions of the hormonal metabolism and - depending on how the thyroid hormones affect the human organism - may become noticeable either as hyperthyroidism or thyroid sub-function.
Iodine blockade is the name given to the „blocking” of the thyroid with non-radioactive iodine by the intake of special iodine tablets as a protective measure in the case of a severe accident in a nuclear power plant. These special iodine tablets prevent radioactive iodine from being stored in the thyroid. The iodine blockade allows you protect yourself against an increased danger of developing thyroid cancer.
Iodine tablets only provide protection against radioactive iodine and against an increased danger of developing thyroid cancer. They do not provide protection against other radioactive material.
Potassium iodide tablets are special iodine tablets which protect the thyroid against radioactive iodine in the case of a severe accident in a nuclear power plant. The potassium iodide tablets which the German emergency response authorities hold in stock contain 65 mg potassium iodide per tablet, which is equivalent to 50 mg iodide. More information here (package insert from the tablet package).
The correct timing of the intake of these iodine tablets is the prerequisite for the iodine blockade to work. If the iodine tablets are taken too late, radioactive iodine may be absorbed by the thyroid. If the iodine tablets are taken too early, the additional non-radioactive iodine may already have been catabolized partially or completely. In the event of a nuclear accident, the emergency response authorities are the first to have access to all relevant information on the release of radioactive iodine and its dispersion in the environment. Therefore, only the emergency response authorities are in a position to decide if iodine blockade is necessary and to make recommendations as to in which areas and at what time the iodine tablets should be taken. In order to ensure the correct functioning of iodine blockade, it is important that you follow the announcements and instructions of the emergency response authorities.
Who should take the iodine tablets in the case of a nuclear accident depends on the age and the location of the persons concerned. Children and adolescents are the main target group for the intake of iodine tablets because of the development and sensitivity of their thyroids. In their announcements the authority may mention which group of people should take the tablets.
Children, whose bodies are in their growth stage, need considerably more thyroid hormones than adults for the control of life processes (including growth itself). The thyroid of a child is therefore considerably more active and, compared to that of an adult, absorbs considerably more iodine. In addition, the thyroid of a child is considerably smaller than that of an adult. Hence, the absorption of radioactive iodine by a child results in a considerably higher exposure of the infantine thyroid tissue than it would in an adult.
The risk of thyroid metabolism dysfunctions increases with age. This so called functional autonomy increases the probability of side effects of iodine blockade. Additionally, as people get older the risk of developing thyroid cancer caused by ionizing radiation considerably decreases. Those aged 45 years and older should therefore refrain from taking iodine tablets, according to the recommendations of the German Commission on Radiological Protection.
As from approximately the 12th week of pregnancy, unborn babies also absorb iodine in their thyroid, pregnant women can protect their child from possible consequences of radioactive iodine by taking iodine tablets.
During the breast feeding period iodine is dispensed in various amounts into the breast milk. However, as these amounts are not sufficient to ensure iodine blockade in the breast-fed child, iodine tablets should also be given to newborns and infants.
The required dosage of iodine tablets may be swallowed with some water. To make it easier for children to take their tablet, the required dosage may also be dissolved in a drink (water, juice, tea). This liquid should then be drunk immediately as it is rather perishable.
The tablets should not be taken on a completely empty stomach.
The correct dosage of iodine tablets for iodine blockade is dependent on a person’s age. It is therefore important that you follow the instructions closely, as you may put your own and your child’s health at risk by administering a dosage that is too high or too low.
Usually a single administration of the recommended dosage is sufficient. Additional tablets should only be taken, if the responsible authority recommends it.
Taking the tablets on an empty stomach may lead to an irritation of the stomach lining. In rare cases, the intake of iodine tablets may trigger allergic reactions, such as: skin rash, itching and burning eyes, a cold, dry cough, diarrhoea, headache, high temperature or similar symptoms.
In individual cases the intake of iodine tablets may cause an iodine-related thyroid-hyperfunction. Symptoms can include an accelerated pulse, sweating, insomnia, shakiness, diarrhoea or weight loss. Please contact your General Practitioner if you notice any of these symptoms.
Persons, who suffer or suffered from thyroid-hyperfunction should only take iodine tablets after having consulted their attending doctor.
If you or your child has been diagnosed with any of the following diseases or allergies, you or your children must not take any iodine tablets: Intolerance to iodine (this rare type of allergy must not be confused with the much more frequent allergy to radiopaque materials); Dermatitis herpetiformis Duhring, also called Duhring-Brocq-Disease (a chronic skin disease whose symptoms include itching, skin eruptions, skin redness, hives and small blisters); Hypocomplementaemic vasculitis (a disease of inflamed blood vessels caused by an allergic reaction). If you are not certain whether you suffer from any of the above diseases please contact your General Practitioner.
Potassium iodide tablets must not be confused with those iodine tablets which are prescribed by General Practitioners for the treatment of thyroid diseases. The concentration of those GP-prescribed tablets is far too low to be used for iodine blockade.
Reversely, those iodine tablets taken for the purpose of iodine blockade must not be used for the treatment of thyroid diseases due to their high iodine concentration. For your own safety, these high-dosage iodine tablets must only be taken on instructions from the emergency response authorities in the case of a nuclear accident.
In Germany enough iodine tablets are held in stock to ensure the sufficient supply of the affected population - especially for children and teenagers. In the case of an accident in a nuclear power plant, iodine tablets will be distributed by the authorities in the affected area.
The communities prepare distribution points. Citizens will be invited via media to pick up their tablets in the distribution points. Please contact your emergency response authority to find out more information.
In such a case the emergency response authorities will look after the distribution of iodine tablets in the same way as if it had happened in a German nuclear power plant (see answer to question no 18).
Iodine tablets should be stored in their original packaging and away from light, humidity and heat (not over 25 °C). The tablets should be kept out of the reach of children.
Please check the expiry date on the packaging. If the storage life is longer than five years the manufacturer is not required to indicate an expiry date. In this case you should note the date of purchase on the packaging.