I-131 is radioactive iodine, or more correctly, an isotope of iodine synthesized artificially. Its half-life is 8 hours, at this time 2 types of radiation are formed - beta and gamma radiation. The substance is absolutely colorless and tasteless, has no aroma.
When is a substance beneficial to health?
In medicine, it is used to treat the following diseases:
- hyperthyroidism - a disease caused by increased activity of the thyroid gland, in which small nodular benign formations are formed in it;
- thyrotoxicosis - a complication of hyperthyroidism;
- diffuse toxic goiter;
- thyroid cancer - during it, malignant tumors appear in the body of the gland, and the inflammatory process joins.
The isotope enters the active cells of the thyroid gland, destroying them - healthy and diseased cells are exposed. Iodine does not affect the surrounding tissues.
At this time, the function of the organ is inhibited.
An isotope is introduced into the body, enclosed in a capsule - or in the form of a liquid - it all depends on the state of the gland, a one-time treatment or course is necessary.
Pros and cons of radioactive iodine treatment for the thyroid gland
Isotope treatment is considered safer than surgery:
- The patient does not need to be anesthetized;
- There is no rehabilitation period;
- Aesthetic defects do not appear on the body - scars and scars; it is especially valuable that the neck is not disfigured - for women, its appearance is of great importance.
The dose of iodine is most often injected into the body once, and if it causes an unpleasant symptom - itching in the throat and swelling, then it is easy to stop it with topical drugs.
The received radiation does not spread to the patient's body - it is absorbed by the only organ that is exposed to.
The amount of radioactive iodine depends on the disease.
In thyroid cancer, reoperation is life-threatening, and radioactive iodine treatment is the best way to stop the recurrence.
Cons and contraindications
The disadvantages of the technique are some of the consequences of the treatment:
- Contraindications to treatment are states of pregnancy and lactation;
- The accumulation of the isotope occurs not only in the tissues of the gland itself - which is natural, but also in the ovaries, so you need to carefully protect yourself within 6 months after the therapeutic effect. In addition, the function of producing hormones, which are necessary for the correct formation of the fetus, may be disrupted, so doctors warn that it is better to postpone plans for the birth of children by 1.5-2 years;
- One of the main disadvantages of the treatment is the absorption of the isotope by the mammary glands, adnexa in women and the prostate in men. Let in small doses, but iodine accumulates in these organs;
- One of the consequences of treating thyroid cancer and hyperthyroidism with radioactive iodine is hypothyroidism, an artificially induced disease that is much more difficult to treat than if it were due to a malfunction of the thyroid gland. In this case, continuous hormonal therapy may be required;
- The consequences of treatment with radioactive iodine can be a change in the function of the salivary and lacrimal glands - the isotope I-131 causes them to narrow;
- Complications can also affect the organs of vision - there is a risk of developing endocrine ophthalmopathy;
- Weight may increase, causeless fatigue and muscle pain may appear - fibromyalgia;
- Chronic diseases are aggravated: pyelonephritis, cystitis, gastritis, vomiting and changes in taste may occur. These consequences are short-lived, diseases are quickly stopped by the usual methods.
Opponents of the method of treating the thyroid gland with iodine largely exaggerate the negative consequences of this method.
If a complication arises - hypothyroidism, then hormonal drugs will have to be taken for life. With untreated hyperthyroidism, you have to take opposite drugs all your life in the same way, and at the same time be afraid that the nodes in the thyroid gland will become malignant.
Weight increases - if you lead an active lifestyle and eat rationally, then the weight will not increase much, but the quality of life will increase and life itself will be longer.
Fatigue, rapid fatigue - these symptoms are inherent in all endocrine disorders, and cannot be directly associated with the use of radioactive iodine.
After the use of the isotope, the risk of developing cancer of the small intestine and thyroid gland increases.
Unfortunately, no one is insured against a relapse of the disease, and the possibility of an oncological process in certain organs - if there were already atypical cells in the body - is high and without the use of radioactive iodine.
The thyroid gland destroyed by radiation cannot be restored.
After surgery, the removed tissue also does not grow.
One more feature of the treatment should be noted, which is considered a negative factor - within 3 days after taking radioactive iodine, patients should be isolated. They pose a danger to others, emitting beta and gamma radiation.
Clothes and things that were in the ward and on the patient must be rinsed with running water or destroyed in the future.
Preparation for the procedure
- It is necessary to prepare for receiving radioactive iodine in advance - already 10-14 days before treatment.
- You should start by changing your diet. Foods with a high iodine content are removed from the diet - the cells should experience iodine hunger. But you should not give up salt at all - it is enough to reduce its amount to 8 g per day.
- If the thyroid gland is absent - it was removed, and at present the disease has recurred, then the accumulation of iodine is taken over by the lungs and lymph nodes - it is on their sensitivity that a test will be carried out - how the isotope is absorbed by the body.
- It is required to abandon all medications used, including hormonal agents - this must be done no later than 4 days before the start of treatment.
- Wounds and cuts should also not be treated with iodine solution, you should not be in the salt room, swim in the sea and breathe the sea air. If you live in a seaside zone, then isolation from external influences is necessary not only after the procedure, but also 4 days before it.
Everyone knows the high danger of radioactive iodine-131, which caused a lot of trouble after the accidents at Chernobyl and Fukushima-1. Even minimal doses of this radionuclide cause mutations and cell death in the human body, but the thyroid gland is particularly affected by it. Beta and gamma particles formed during its decay are concentrated in its tissues, causing severe radiation and the formation of cancerous tumors.
Radioactive iodine: what is it?
Iodine-131 is a radioactive isotope of common iodine, called "radioiodine". Due to its rather long half-life (8.04 days), it quickly spreads over large areas, causing radiation contamination of soil and vegetation. I-131 radioiodine was first isolated in 1938 by Seaborg and Livingood by irradiating tellurium with a flux of deuterons and neutrons. Subsequently, it was discovered by Abelson among the fission products of uranium and thorium-232 atoms.
Sources of radioiodine
Radioactive iodine-131 is not found in nature and enters the environment from technogenic sources:
- Nuclear power plants.
- Pharmacological production.
- Atomic weapons tests.
The technological cycle of any power or industrial nuclear reactor includes the fission of uranium or plutonium atoms, during which a large amount of iodine isotopes accumulates in the facilities. Over 90% of the entire family of nuclides are short-lived isotopes of iodine 132-135, the rest is radioactive iodine-131. During normal operation of a nuclear power plant, the annual release of radionuclides is small due to the filtration carried out to ensure the decay of nuclides, and is estimated by specialists at 130-360 Gbq. If there is a breach of the tightness of a nuclear reactor, radioiodine, having high volatility and mobility, immediately enters the atmosphere along with other inert gases. In the gas-ash release, it is mostly contained in the form of various organic substances. In contrast to inorganic iodine compounds, organic derivatives of the iodine-131 radionuclide pose the greatest danger to humans, since they easily penetrate the lipid membranes of the cell walls into the body and are subsequently carried through the blood to all organs and tissues.
Major accidents causing iodine-131 contamination
In total, there are two major accidents at nuclear power plants that have become sources of radioiodine contamination of large areas - Chernobyl and Fukushima-1. During the Chernobyl disaster, all the iodine-131 accumulated in the nuclear reactor was released into the environment with the explosion, which led to radiation contamination of a zone with a radius of 30 kilometers. Strong winds and rains carried radiation all over the world, but the territories of Ukraine, Belarus, southwestern regions of Russia, Finland, Germany, Sweden, Great Britain were especially affected.
In Japan, the explosions at the first, second, third reactors and the fourth power unit of the Fukushima-1 NPP occurred after the strongest earthquake. As a result of the violation of the cooling system, several radiation leaks occurred, leading to a 1250-fold increase in the number of iodine-131 isotopes in seawater at a distance of 30 km from the nuclear power plant.
Nuclear weapons testing is another source of radioiodine. So, in the 50-60s of the twentieth century in the territory of the state of Nevada in the United States, explosions of nuclear bombs and shells were carried out. Scientists noticed that the I-131 formed as a result of the explosions fell out in the nearest regions, and in semi-global and global fallouts it was practically absent due to the short half-life. That is, during migrations, the radionuclide had time to decompose before falling along with precipitation onto the Earth's surface.
Biological effects of iodine-131 on humans
Radioiodine has a high migratory ability, easily penetrates the human body with air, food and water, and also enters through the skin, wounds and burns. At the same time, it is quickly absorbed into the blood: after an hour, 80-90% of the radionuclide is absorbed. Most of it is absorbed by the thyroid gland, which does not distinguish stable iodine from its radioactive isotopes, and the smallest amount is absorbed by muscles and bones.
By the end of the day, up to 30% of the total incoming radionuclide is recorded in the thyroid gland, and the accumulation process directly depends on the functioning of the organ. If hypothyroidism is observed, then radioiodine is absorbed more intensively and accumulates in the tissues of the thyroid gland in higher concentrations than with a reduced function of the gland.
Basically, iodine-131 is removed from the human body with the help of the kidneys within 7 days, only a small part of it is removed along with sweat and hair. It is known to evaporate through the lungs, but it is still not known how much of it is excreted from the body in this way.
Iodine-131 toxicity
Iodine-131 is a source of dangerous β- and γ-radiation in a ratio of 9: 1, capable of causing both light and severe radiation injuries. Moreover, the most dangerous is the radionuclide that enters the body with water and food. If the absorbed dose of radioiodine is 55 MBq / kg of body weight, acute irradiation of the whole organism occurs. This is due to the large area of \u200b\u200bbeta-irradiation, which causes a pathological process in all organs and tissues. The thyroid gland is especially severely damaged, intensively absorbing radioactive isotopes of iodine-131 together with stable iodine.
The problem of the development of thyroid pathology became relevant during the accident at the Chernobyl nuclear power plant, when the population was exposed to I-131. People received large doses of radiation not only by inhaling contaminated air, but also by consuming fresh cow's milk with a high content of radioiodine. Even the measures taken by the authorities to exclude natural milk from the sale did not solve the problem, since about a third of the population continued to drink milk from their own cows.
It's important to know!
Especially strong irradiation of the thyroid gland occurs when dairy products are contaminated with iodine-131 radionuclide.
As a result of radiation, the function of the thyroid gland decreases with the subsequent possible development of hypothyroidism. In this case, not only is the thyroid epithelium damaged, where hormones are synthesized, but also the nerve cells and vessels of the thyroid gland are destroyed. The synthesis of the necessary hormones sharply decreases, the endocrine status and homeostasis of the whole organism are disrupted, which can serve as the beginning of the development of cancerous tumors of the thyroid gland.
Radioiodine is especially dangerous for children, since their thyroid glands are much smaller than that of an adult. Depending on the age of the child, the weight can range from 1.7 g to 7 g, while as in an adult it is about 20 grams. Another feature is that radiation damage to the endocrine gland can be latent for a long time and only manifest itself during intoxication, illness, or during puberty.
Children under one year of age who receive a high dose of radiation with the isotope I-131 are at high risk of developing thyroid cancer. Moreover, the high aggressiveness of tumors has been clearly established - cancer cells penetrate into the surrounding tissues and blood vessels within 2-3 months, metastasize to the lymph nodes of the neck and lungs.
It's important to know!
In women and children, thyroid tumors occur 2-2.5 times more often than in men. The latent period of their development, depending on the dose of radioiodine received by a person, can reach 25 or more years, in children this period is much shorter - on average about 10 years.
"Useful" iodine-131
Radioiodine, as a remedy against toxic goiter and thyroid cancers, began to be used as early as 1949. Radiation therapy is considered a relatively safe method of treatment, without it, various organs and tissues are affected in patients, the quality of life deteriorates and its duration decreases. Today, the isotope I-131 is used as an additional tool to combat the recurrence of these diseases after surgery.
Like stable iodine, radioiodine is accumulated and retained for a long time by the cells of the thyroid gland, which use it to synthesize thyroid hormones. As tumors continue to perform hormone-forming functions, they accumulate isotopes of iodine-131. When they decay, they form beta particles with a range of 1-2 mm, which locally irradiate and destroy the cells of the thyroid gland, and the surrounding healthy tissues are practically not exposed to radiation.
Iodine 131 is a beta, gamma emitter with a half-life of 8.1 days. The energy of gamma radiation is 0.364 MeV, the energy of beta radiation is 0.070 MeV. The total activity of drugs used for diagnostic purposes is from 2 to 5 mccuries (300 mccuries are allowed only when scanning the liver and kidneys). Upon receipt of 1 μcurie of iodine in the thyroid gland, a dose of 1.5-2 rad is created. The eligibility of using various amounts of iodine for diagnostic purposes is determined by clinical indications (F.M. Lyass, 1966). Regardless of the route of intake, iodine rapidly accumulates in the body, while up to 90% is concentrated in the thyroid gland. Iodine is excreted in urine and feces. It can also be found in saliva (immediately after administration). The maximum allowable amount for chronic intake is 0.6 μcurie; this value is well substantiated by clinical observations as safe for the human body by all criteria.
The practice of using sufficiently large amounts of radioactive iodine for therapeutic purposes (up to 100 μcurie), the experience of the Windskell accident (England), data on the fallout of radioactive fallout from a nuclear explosion on the Marshall Islands allow us to assess the degree of danger of accidental ingestion of the isotope in a wide range of doses.
In accordance with the nature of the selective distribution of iodine, clinical manifestations, depending on the dose, vary from transient changes in the function of the thyroid gland with an increase in the possibility of its blastoma metaplasia in the long term to deep, early onset destruction of the gland tissue, which may be accompanied by general clinical manifestations of radiation sickness, including disorders hematopoiesis. Due to the relatively rapid formation of radiation exposure, the main symptoms develop, as a rule, in a relatively early period - in the first 1-2 months.
According to D.A.Ulitovskiy (1962) and N.I.Ulitovskaya (1964), selective irradiation and damage to the thyroid gland and its neuroreceptor apparatus take place with a single intake of 1-3 μuri I131, which corresponds to a local dose of 1000-3000 rad. Integral doses throughout the body are close to those generated by irradiation from external gamma sources at a dose of 7-13 r; there are no signs of distinct general reactions in these cases.
The development of clinical manifestations with the possibility of a lethal outcome with changes in blood typical of radiation sickness is observed upon admission in a short time of 300-500 μi I131, which creates a total radiation dose of the order of 300-570 rad. Total activities of 20-50 mc of iodine lead to an intermediate group of clinical effects. It should be remembered that the decisive contribution to the dose is given by the beta-radiation of iodine, i.e., there is a certain uneven distribution of the dose in the volume of the gland and the preservation, due to this, of individual intact sections of the epithelium of the follicles. When using isotopes I132 and I134, which are powerful gamma emitters, the biological effect is higher due to the uniformity of irradiation of the gland tissue.
Iodine-131 is a radionuclide with a half-life of 8.04 days, beta and gamma emitter... Due to its high volatility, almost all of the iodine-131 present in the reactor (7.3 MCi) was released into the atmosphere. Its biological effect is associated with the peculiarities of the functioning of the thyroid gland. Its hormones - thyroxine and triiodothyroyaine - contain iodine atoms. Therefore, the thyroid gland normally absorbs about 50% of the iodine entering the body.Naturally, iron does not distinguish radioactive isotopes of iodine from stable ones. ... The thyroid gland of children is three times more active in absorbing radioiodine that has entered the body. In addition, iodine-131 easily crosses the placenta and accumulates in the fetal gland.
The accumulation of large amounts of iodine-131 in the thyroid gland leads to thyroid dysfunction. The risk of malignant tissue degeneration also increases. The minimum dose at which there is a risk of developing hypothyroidism in children is 300 glad, in adults - 3400 glad. The minimum doses at which there is a risk of developing thyroid tumors are in the range of 10-100 rad. The risk is greatest at doses of 1200-1500 glad. Women are four times more likely to develop tumors than men, and children are three to four times more likely to develop tumors than adults.
The magnitude and rate of absorption, the accumulation of radionuclide in organs, and the rate of excretion from the body depend on age, gender, stable iodine content in the diet and other factors. In this regard, when the same amount of radioactive iodine enters the body, the absorbed doses differ significantly. Especially large doses are formed in the thyroid gland of children, which is associated with the small size of the organ, and can be 2-10 times higher than the radiation dose of the gland in adults.
The intake of stable iodine preparations effectively prevents the ingress of radioactive iodine into the thyroid gland. In this case, the iron is completely saturated with iodine and rejects the radioisotopes that have entered the body. Taking stable iodine even 6 hours after a single intake of 131I can reduce the potential dose to the thyroid gland by about half, but if iodine prophylaxis is postponed for a day, the effect will be small.
The intake of iodine-131 into the human body can occur mainly in two ways: by inhalation, i.e. through the lungs, and orally through ingested milk and leafy vegetables.
The effective half-life of long-lived isotopes is determined mainly by the biological half-life, for short-lived isotopes - by the half-life. The biological half-life is diverse - from several hours (krypton, xenon, radon) to several years (scandium, yttrium, zirconium, anemones). The effective half-life ranges from several hours (sodium-24, copper-64), days (iodine-131, phosphorus-23, sulfur-35), to tens of years (radium-226, strontium-90).
The biological half-life of iodine-131 from the whole organism is 138 days, the thyroid gland is 138, the liver is 7, the spleen is 7, the skeleton is 12 days.
Long-term consequences - thyroid cancer.
Dosage Form: & nbspcapsules
Composition:Per capsule:
Active substance:
Iodine-131 0.5; 1.0; 2.0; 4.0 GBq (as sodium iodide).
Excipientsand:
Sodium diphosphate 237 mg.
Capsule (size 1) (body: titanium dioxide - 2.00%, gelatin - up to 100%;
cap: titanium dioxide - 1.33%, sunset yellow dye - 0.44%, gelatin - up to 100%)
Description:Hard gelatin capsule (size 1), consisting of a white body and an orange cap. The contents of the capsule are white powder.
Pharmacotherapeutic group:Radiopharmaceutical therapeutic agent ATX: & nbspV.09.F.X Other radiopharmaceuticals for the diagnosis of thyroid diseases
Pharmacodynamics:Physicochemical characteristics
Sodium iodide, 131 I - the drug is obtained by applying a solution of sodium iodide, 131 I to sodium diphosphate in the capsule. The activity of iodine-131 is 0.5; 1.0; 2.0; 4.0 GBq at the specified date and time of drug delivery. Iodine-131 decays with a half-life of 8.02 days; the most intense component of gamma radiation has an energy of 365.0 keV (81.7%), β-radiation - 606.0 keV (89.7%).
Pharmacodynamics
A capsule, introduced on an empty stomach through the mouth with 25-30 ml of distilled water, dissolves in the stomach, on average, within 15 minutes, sodium iodide, 131 I enters the blood with a half-life of 8-10 minutes from the stomach cavity. Subsequently, radioactive iodine-131 accumulates mainly in the thyroid gland.
Radioactive iodine-131 is selectively captured by the thyroid gland and, due to P-radiation, which has a short range of particles, causes cell destruction with minimal effect on the surrounding healthy tissues.
Pharmacokinetics:The kinetics of absorption of iodine-131 by the thyroid gland (relative to the amount administered) is, on average, after 2 hours - 10%, after 4 hours - 19%, after 24 hours - 27%. During the day, about 60% of the drug is excreted in the urine and feces. Values \u200b\u200bof quantities
accumulation and rate of elimination of the drug depend on the functional state of the thyroid gland and the age and sex of the patient. Indications:The drug is used to treat thyrotoxicosis in diffuse and multinodular toxic goiter, as well as for the treatment of thyroid cancer and its metastases.
Contraindications:Hypersensitivity, nodular goiter, retrosternal goiter, euthyroid goiter, mild forms of thyrotoxicosis, mixed toxic goiter, hematopoietic disorders (leukopoiesis and thrombocytopoiesis), severe hemorrhagic syndrome, gastric ulcer and 12 duodenal ulcer, pregnancy, lacrimation period age up to 20 years.
Carefully:Age from 20 to 40 years old. Method of administration and dosage:The drug "Sodium iodide, 131 I" is intended for oral administration.
For treatment differentiated thyroid cancer, as well as distant metastases. Treatment is carried out 3-4 weeks after thyroidectomy or discontinuation of L-thyroxin 20 days before drug administration. The capsule is inserted through the mouth at the rate of 37 MBq per kilogram of body weight, and patients are transferred to specialized wards, which are equipped with an autonomous ventilation and sewerage system connected to special treatment facilities. Patients are taken out of the "closed" mode when the gamma radiation power is reduced to the permissible radiation safety standards (ZmkSv / h).
The value of a single therapeutic activity of iodine-131 for adults is 37 - 56 MBq per kilogram of body weight. The duration of intervals between injections of the drug is 3 - 6 months.
For the treatment of thyrotoxicosis with diffuse and multinodular toxic goiter
... Radioactive iodine-131 is captured only by the tissue of the thyroid gland, causing cell destruction, and excreted in the urine with minimal impact on the surrounding healthy tissue.Currently, there are two most common methods for calculating the input activity of iodine-131.
1. Individual calculation based on the volume of the thyroid gland, the rate of uptake of iodine-131 during the diagnostic scan 24 hours after taking the drug and the specified activity per gram of tissue (range from 0.1 to 0.3 MBq / g) according to the formula:
And in \u003dAz x V / C x 10, where
And 3 - given activity, MBq / g; V is the volume of the thyroid gland, cm 3; C - the rate of capture of iodine-131 in 24 hours after drug administration 10 - coefficient.
2. Appointment of fixed activity of iodine-131:
190 MBq - small glands,
380 MBq - medium-sized glands,
570 MBq - large glands
Before starting treatment, a preliminary determination of the absorption of iodine-131 by the thyroid gland is necessary, which guarantees the correctness of treatment, excludes the possibility of an error associated with the use of fixed activity in a patient with a large but poorly absorbing iodine-131 gland.
With the therapeutic use of the drug, a prerequisite is constant monitoring of the state of the peripheral blood.
Radiation loads on the patient's organs and tissues when using the drug "Sodium iodide, 131 I".| Absorbed dose, mGy / MBq |
|
| red bone marrow | |
| bladder | |
| pancreas | |
| spleen | |
| small intestine | |
| thyroid | |
| Equivalent dose, mSv / MBq |
In the treatment of thyrotoxicosis and metastases of thyroid cancer, exacerbations of thyrotoxicosis, the occurrence of hypothyroidism and myxedema, the appearance or intensification of exophthalmos, radiothyroiditis, nausea, vomiting, thrombocytopenia, leukopenia, acute gastritis, amenorrhea, ulcerative cystitis, changes in the skin, parotitis areas of the thyroid gland, pharyngeal mucosa and larynx. Treatment is symptomatic.
When using the drug, it is possible to suppress bone marrow hematopoiesis, the restoration of which is carried out by known means: leucogen, methyluracil,.
Overdose:An overdose of the drug is unlikely due to careful monitoring of the administered activity in a specialized hospital.
Interaction:In the dosages used, interactions with other drugs were not observed.
Special instructions:Treatment with this drug (radiotherapy) should be carried out under the supervision of a radiologist in specialized departments with special sewage systems or conditions for the collection and storage of radioactive urine and feces, in accordance with the "Basic Sanitary Rules for Ensuring Radiation Safety" (OSPORB-99 / 20Yu), " Radiation Safety Standards "(NRB-99/2009) and" Hygienic Requirements for Ensuring Radiation Safety During Radiation Therapy Using Open Radionuclide Sources "(SanPiN 2.6.1.2368-08).
Impact on the ability to drive vehicles. Wed and fur .:not described Release form / dosage:Capsules with an activity of 0.5; 1.0; 2.0; 4.0 GBq at the specified date and time of delivery. The permissible deviation of the values \u200b\u200bof the activity of iodine-131 in each capsule from the nominal is ± 10%.
Packaging: Each capsule is placed in vials for medicines made of glass of the 1st hydrolytic class with a capacity of 10 or 15 ml, hermetically sealed with rubber medical stoppers and crimped with aluminum caps. The bottle, passport, instructions for use are placed in a transport packaging set for radioactive substances. Storage conditions:At temperatures from 15 to 25 ° C. In accordance with the current "Basic Sanitary Rules for Ensuring Radiation Safety" (OSPORB - 99/2010).
Shelf life:20 days from the date of manufacture. Do not use after the expiration date.
Terms of dispensing from pharmacies:For hospitals Registration number:LSR-003509/07 Registration date:31.10.2007 / 25.12.2017 Expiration date:Indefinite Marketing Authorization Holder:FSUE "Federal Center for Design and Development of Nuclear Medicine Facilities" FMBA of Russia Russia Manufacturer: & nbspRussia
Date of information update: & nbsp26.05.2018 Illustrated instructions
