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Guidelines for Iodine Prophylaxis following Nuclear Accidents
Update 1999, World Health Organization, Geneva

6. Logistics of stable iodine prophylaxis

6.1 Chemical form

Stable iodine can be used either as potassium iodide (KI) or potassium iodate (KIO3). KI is the preferred alternative, since KIO3 has the disadvantage of being a stronger intestinal irritant (19). There is no decisive difference in shelf life between KIO3 and KI. If storage conditions are adequate, the expected shelf life of the tablets is at least 5 years. After 5 years the iodine content may be checked and the shelf life extended, if indicated.

6.2 Formulation, storage and packaging

Stable iodine can be given in either doubly scored tablet or liquid form. Tablets have the advantage of easy storage and distribution, including predistribution. Also, stable iodine is likely to cause less gastrointestinal irritation if administered in tablet form. Tablets can be crushed and mixed with fruit juice, jam, milk or similar substance.

Tablets should be stored protected from air, heat, light and moisture. Age-dependent dosage and contraindications should be on the labelling.

Tablets packed in a hermetic alufoil and kept in a dry and cool place preserve fully their iodine content for 5 years (20).

6.3 Availability, predistribution and distribution

As there is only limited time for implementation of prophylaxis, prompt availability of the tablets to individuals has to be ensured if they are to be at their most effective. In the vicinity of nuclear reactors, predistribution to households should be seriously considered, taking into account plans for evacuation and sheltering, with provision for storage in places that can be controlled by the responsible authorities. Clear instructions should be issued with the tablets, and public awareness of the procedures should be monitored on a regular basis. Medical personnel likely to be consulted by the public should be provided with more detailed information. At greater distances from the site of release there is likely to be more time for decision-making. If predistribution to households is not considered feasible, stocks of stable iodine should be stored strategically at points that may include schools, hospitals, pharmacies, fire stations, police stations and civil defence centres. Widespread storage may be warranted at considerable distances from the potential accident site. Storage should preferably be at places where proper stock control is standard practice. Planning should consider the use of redundant distribution areas to minimize delays in implementing stable iodine prophylaxis. Due consideration should also be given to whether the benefits of stable iodine distribution outweigh the disadvantages associated with any additional exposure of responsible emergency personnel.

National authorities are advised that, because of the benefits of stable iodine prophylaxis and the generally minimal risks of side effects, voluntary purchase of iodine tablets by the general public should be allowed. However, within the framework of the overall nuclear emergency plan, the responsibility for distribution of stable iodine and instructing the public on how to use it should still be clearly assigned to the appropriate authorities.

6.4 Dosage and contraindications

For adequate suppression, the dosage scheme given in Table 2, which is based on a single dose for adults of 100 mg of iodine, is recommended.

The tablet divisions indicated in Table 2 are easy to achieve with a tablet stamped by a cross, except that the exact dosage of 1/ 8 tablet required for neonates is difficult to ensure. However, for neonates over 1 week of age living at home, an approximate division would be satisfactory. The most sensitive group of the newborn, those less than 1 week old, should preferably have a more exact dosage. This can be achieved with KI solution freshly prepared from crystals. It is, therefore, recommended that maternity wards keep KI in storage in crystal form.

As an alternative, tablets containing 50 mg of iodine (65 mg KI or 85 mg KIO3) can be used, correspondingly doubling the tablet dosage indicated in Table 2. It is recognized that some iodine tablets are too small to subdivide effectively and it is recommended that tablets of sufficient size be manufactured.

The contraindications for use of stable iodine are:

past or present thyroid disease (e. g. active hyperthyroidism)

known iodine hypersensitivity

dermatitis herpetiformis

hypocomplementaemic vasculitis.

These should be clearly stated on the labelling.

6.5 Timing of administration and duration of prophylaxis

To obtain full effectiveness of stable iodine for thyroidal blocking requires that it be administered shortly before exposure or as soon after as possible. However, iodine uptake is blocked by 50% even after a delay of several hours. Fig. 1 shows the effectiveness of thyroid blocking achieved by administering stable iodine at different times before or after a 4-h exposure to radioiodine.

To protect against inhaled radioactive iodine, a single dose of stable iodine would generally be sufficient, as it gives adequate protection for one day. This may well be enough to protect from inhaled radioactive iodine present in a passing cloud. In the event of a prolonged release, however, repeated doses might be indicated.

Fig. 1. Averted dose as a function of time stable iodine is administered to a 4-h intake of 131 I for different dietary iodine intakes

[Note from KI4U: Unable to capture this graph to HTML for display here. To view it with an Adobe Acrobat Reader, get the original PDF file here Guidelines for Iodine Prophylaxis following Nuclear Accidents. If you know how to capture this graphic in a form we can then display here, too, please let us know. Thank you.]

In some circumstances stable iodine administration may also be practical in limiting the dose to the thyroid from ingested radioactive iodine, especially to children via the milk pathway where alternative sources cannot be found. In that case, a daily dose of stable iodine may be given for the time period needed to those children who show no adverse reaction. Repeated administrations should not be given to neonates, or to pregnant or lactating women (see section 3.2).

Due consideration should be given, in preparing emergency plans, to mitigating any adverse psychosocial reactions to the implementation of iodine prophylaxis. To avoid public concern, distribution and instructions to different age groups must be orderly and consistent. There are advantages in consulting with neighbouring countries with regard to their national policy in order to avoid discrepancies of approach, especially where reactors are close to national borders.



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