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