Effects of 99mTc on the electrochemical properties of thiamazole in vitro

Thiamazole inhibits the thyroid hormone synthesis and does not inactivate the existing thyroxine and triiodothyronine that circulate in the blood. In this paper Thiamazole electrochemical behavior was monitored by cyclic voltammetry on glassy carbon (GC) electrode in the absence and presence of sodium pertechnetate (99mTc). The influence of different Thiamazole concentrations without and in the presence of radiopharmaceutical 99mTc, the effect of the number of scan cycles, and the effect of 99mTc activity on the appearance of cyclic voltammograms were examined. The results show that there is an observed increase in the reduction peak current with an increase of Thiamazole concentration. It was found that the concentration of the tested drug had a significant effect on its redox characteristics. The results obtained show that the application of different concentrations of sodium pertechnetate exhibits the inhibitory properties of the used radiopharmaceutical on the drug in the treatment of thyroid gland disease.

Use of 99m Tc in The Field of Radiofarmation: A Review

A B S T R A C TTechnetium-99m ( 99m Tc) has been applied in nuclear medicine as a radiopharmacyfor both diagnosis and therapy. 99m Tc is obtained from a 99 Mo/ 99m Tc (half-life 66 h)generator in the form of sodium pertechnetate (Na[ 99m TcO 4 ]) by decaying to 99 Tc for 6hours and emitting gamma energy rays (Eɤ = 140 keV). This radionuclide has anelectron configuration of 4d 5 5s 2 , which will form complexes with different ligandsand have oxidation rates from +1 to +7. The coordinated complex of technetium-99mhas been utilized in nuclear medicine in tissues and organs (thyroid, red and whiteblood cells, kidneys, brain, myocardial, and bone). The resulting kit production musthave based on Good Manufacturing Practice, which consists of batch planning,washing, sterilization of glassware and stopper, starting material, preparation oflarge quantities of the solution, sterile filtration, dispensing, crimping, a summary ofprocess control, quarantine, packaging and leaving the production premises.

Experience in Validation of Methods for Determination of Radiochemical Impurities in Radiopharmaceuticals

Most important quality attributes of any radiopharmaceutical (RPh) are its radiochemical purity (RCP) or content of radiochemical impurities (RCIs) that have to comply with respective norms and limits. However, at present, there is no unified approach to validation of analytical methods in the context of highly radioactive samples.The aim of the study was to develop an approach to validation of methods for determination of RCI content in RPhs.Materials and methods: the authors determined the content of RCIs in a radiopharmaceutical formulation containing a complex of technetium-99m and methylenediphosphonic acid by the radiometric method after isolation of impurities from the main compound by thin-layer chromatography using silica gel and methyl ethyl ketone (for sodium pertechnetate determination) and silica gel and 13.6% sodium acetate solution (for determination of hydrolysed reduced technetium-99m). The radioactivity was registered by a chromatogram scanner with a detector of gamma-rays with energies from 0.05 to 1.5 MeV.Results: the paper analyses existing official approaches to validation of analytical procedures and compares them with the results of experimental studies described in available publications. It assesses the validation parameters for compliance with the acceptance criteria set forth in the current regulations and substantiates selectivity of chromatographic determination of impurities under the selected test conditions. Coefficients of variation for repeatability, reproducibility, and accuracy did not exceed 4.5, 2.8, and 8.9%, respectively, given the relative error of not more than 10.5%. The study demonstrated signal linearity for the 10-fold dilution of the standardised sodium pertechnetate solution, it also demonstrated correspondence between the applied and detected radioactivity when performing the test in the impurity content range of 0.5–5%. The validation procedure was associated with significant radiation burden for the personnel of the quality control laboratory.Conclusions: the authors suggested a methodological approach to validation of methods for determination of RCI content in technetium-99m-based RPhs. This approach may be used in the development of a guideline on validation of analytical methods for RCP/RCI determination in RPhs, or for introduction of relevant sections into existing documents.

Radiopharmaceuticals for diagnosis in nuclear medicine: a short review

Radiopharmaceuticals are radioactive compounds which have a bound radionuclide in their structure, whose purpose is directing the radionuclide to a location to be treated or to obtain images. Nuclear medicine is the medical specialty that employs radiopharmaceuticals, which has presented itself as a tremendously useful ally for medicine assisting in various diagnoses and treatments, especially for cancer. The general objective of this work is to identify the main radionuclides and metal complexes currently used as radiopharmaceuticals. The main metal complexes used as radiopharmaceuticals are compounds of technetium (99mTc) like sodium pertechnetate and methylenediphosphonate MDP-99mTc and other compounds of indium (111In), thallium (201Tl), gallium (67Ga, 68Ga), iodine (123I and 131I), chromium (51Cr), sulphur (35S), phosphorus (32P), fluorine (as fluorodeoxyglucose, 18F-FDG and sodium fluorine, Na18F), which are widely used in the nuclear medicine for diagnosis by imaging. They have been of great importance for the early diagnosis of numerous diseases, mainly cancer.Currently, technetium compounds are the majority of radiopharmaceuticals used in all countries. In Brazil, Institute of Energy and Nuclear Research (IPEN) is one of the most important distributors of radiopharmaceuticals, producing, importing and distributing them to clinics and hospitals over the country.

Predictive value of scintigraphic (semi-)quantitative thyroid parameters on radioiodine therapy outcome in hyperthyroid cats

Objectives The outcome of radioiodine therapy in hyperthyroid cats is suspected to be influenced by multiple factors. The degree of activity of the thyroid gland, represented by uptake of sodium pertechnetate or tracer activities of radioiodine by the thyroid gland on thyroid scintigraphy, has been suggested in the literature as one of those. Thyroid gland pertechnetate uptake can be represented by (semi-)quantitative factors such as the thyroid to salivary gland (T/S) ratio, the thyroid to background (T/B) ratio and the percentage technetium uptake by the thyroid glands (%TcU). The aim of this study was to investigate a possible relationship between these thyroid scan parameters and radioiodine therapy outcome. Methods Sodium pertechnetate thyroid scans of 75 hyperthyroid cats were retrospectively evaluated and statistical analysis was performed with and without correction for injected radioiodine activity. Three different background regions of interest (ROIs) were used to calculate the T/B ratio and %TcU: ‘neck’, ‘circle’ and ‘copy ROI’. Results Higher T/S ratios were found to be significantly related to a persistent hyperthyroid outcome in both analyses. For the T/S ratio, a threshold value of 5.4 was determined, with a sensitivity of 73% and a specificity of 59%. An increased risk for persistent hyperthyroidism compared with a final euthyroid outcome with an increased T/Bcircle ratio was only found to be significant without correction for the activity of radioiodine administered. For the %TcU no statistical significance was reached. Regarding a low total thyroxine outcome, no significant relationships with any of the investigated parameters were found. Conclusions and relevance The findings of this study suggest that semi-quantification of thyroid gland uptake is best performed using the T/S ratio. A T/S ratio ⩾5.4 is a possible indicator for an increased risk of persistent hyperthyroidism.