Source: Medicines & Healthcare Products Regulatory Agency (GB) Revision Year: 2020 Publisher: hameln pharma ltd, Nexus, Gloucester Business Park, Gloucester, GL3 4AG, UK
Hypersensitivity to potassium iodide (see also sections 4.2 and 4.5) or to any of the excipients listed in section 6.1.
In cases of exposure to radioiodine from nuclear accidents, dosing of potassium iodide should be based on emergency plans and predetermined operational intervention levels. Risk benefit of administration of stable radioiodine should be considered for the different age groups at risk. Pregnant and lactating women, neonates, infants and children should be treated first. A single dose of potassium iodide gives adequate protection for one day. Prolonged exposure may require repeat dosing, however repeat dosing in the neonate, and in pregnant and lactating women should be avoided (see section 4.2). Iodine prophylaxis is used against inhaled radioiodine and should not be the main prophylaxis for ingested contamination.
Patients with thyrotoxicosis treated medically, or patients with a past history of thyrotoxicosis treated medically who are now off treatment and apparently in remission, may be at risk.
Iodine induced hyperthyroidism may be precipitated in patients with asymptomatic nodular goitre or latent Graves' disease, who are not under medical care.
Potassium salts should be given cautiously to patients with renal or adrenal insufficiency, acute dehydration or heat cramp.
Care should be exercised if potassium salts are given concomitantly with potassium-sparing diuretics, as hyperkalaemia may result (see section 4.5).
The potential benefit of iodine prophylaxis is greatest in the young. The thyroid of the foetus, neonate and young infant has a higher yearly thyroid cancer risk per unit dose of radioactive iodine than the thyroid of an adult.
Potassium iodide prophylaxis is not usually indicated in adults over 40 unless doses to the thyroid from inhalation rise to levels threatening thyroid function, that is of the order of about 5 Gy. The risk of thyroid cancer is extremely low in this group whereas the incidence of thyroid disease is higher in this group therefore the risk of iodine induced thyroid complications are higher.
Neonates in the first days of life are at particular risk from exposure to radioactive iodine and blocking of thyroid function by overload of potassium iodide. The fraction of radioactive uptake is fourfold greater than all other age groups. The neonatal thyroid is especially sensitive to functional blocking caused by overload of potassium iodide. Transient hypothyroidism during this early period of brain development can result in loss of intellectual capacity. If stable iodine is given to neonates close follow up of thyroid function is essential. For neonates who have been administered potassium iodide in the first few weeks of life TSH levels and, if necessary, T4 levels should be monitored and appropriate replacement therapy given.
Several drugs, such as captopril and enalapril can cause hyperkalaemia and this effect may be enhanced if potassium iodide is also administered.
The effect of quinidine on the heart is increased by increased plasma concentration of potassium.
Hyperkalaemia results from the interaction between potassium salts and potassium sparing diuretics such as amiloride or triamterene or aldosterone antagonists (see section 4.4).
The effects of iodine and iodides on the thyroid may be altered by other compounds which may also have an effect on the thyroid, including amiodarone and lithium. The hypothyroid and goitrogenic effects of lithium carbonate and iodides can be additive if they are given concurrently.
Teratogenic effects such as congenital goitre and hypothyroidism have been reported when iodides are administered to pregnant women.
Prophylactic administration of iodide to the pregnant mother should also be effective for the foetus.
Throughout pregnancy the number of doses of potassium iodide should be kept to a minimum and repeat doses should be avoided (see section 4.2). In areas of iodine deficiency prolonged dosage could lead to maternal or foetal thyroid blockage with possible consequences for foetal development. If potassium iodide is administered late in pregnancy, the thyroid function of the new-born should be monitored. This is generally met by routine screening in the neonatal period. For neonates who have been administered potassium iodide in the first few weeks of life TSH levels and, if necessary, T4 levels should be monitored and appropriate replacement therapy given.
Pregnant women with active hyperthyroidism must not take potassium iodide because of the risk of foetal thyroid blockage.
Iodine is actively transported into breast milk, however those breast feeding should continue to do so (see section 5.2). Lactating women should avoid repeat doses (see section 4.2).
No human data on the effect of active substance potassium iodide on fertility are available. There is no preclinical information available on the effect of the active substance potassium iodide on mating or fertility.
ThySat 65 mg tablets have no or negligible influence on the ability to drive and use machines.
Undesirable effects are listed by MedDRA System Organ Classes.
Assessment of undesirable effects is based on the following frequency groupings: Very common: ≥1/10, Common: ≥1/100 to <1/10, Uncommon: ≥1/1,000 to <1/100, Rare: ≥1/10,000 to <1/1,000, Very rare: <1/10,000, Not known: cannot be estimated from the available data.
Not known: Gastrointestinal disturbance (including nausea). Taste disturbance (including metallic taste).
Not known: Hypersensitivity reactions such as skin rashes, swollen salivary glands, headache, and bronchospasm can be mild or severe and may be dose dependent.
Not known: Hyperthyroidism, iodine induced autoimmunity (Grave’s and Hashimoto type), toxic nodular goitre and iodine-induced hypothyroidism have been reported as side effects of iodine therapy. An overactive thyroid gland, thyroiditis, and an enlarged thyroid gland with or without development or myxoedema have also been reported.
Continued administration may lead to mental depression, nervousness, sexual impotence and insomnia.
Reporting suspected adverse reactions after authorisation of the medicinal product is important. It allows continued monitoring of the benefit/risk balance of the medicinal product. Healthcare professionals are asked to report any suspected adverse reactions via Yellow Card Scheme. Website: www.mhra.gov.uk/yellowcard or search for MHRA Yellow Card in the Google Play or Apple App Store.
Not applicable.
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