Intramuscular iodine injections

Intramuscular iodine injections Numerous studies have confirmed that iodine supplementation by injection before a woman becomes pregnant can prevent endemic cretinism and that a single injection can prevent goitre for up to 3-4 years. Other documented benefits of maternal supplementation observed in several controlled studies include reduced infant and young-child mortality, improved birth weight, and better manual function in children born to iodine-supplemented mothers. 

Larsen SW, Rinvar E, Svendsen O, et al. Determination of the disappearance rate of iodine-125 labelled oils from the injection site after intramuscular and subcutaneous administration to pigs. Int ] Pharm 2001 230(1-2) 67-75. 

A considerable advance in the management of thyroid cancer has resulted from the introduction of recombinant human TSH (thyrogen). A dose of 0.9 mg is administered intramuscularly, followed by an identical dose 24 hours later. The serum thyroglobuLin is then measured 48-72 hours after the second TSH injection this has become the preferred diagnostic test for following patients with differentiated thyroid cancer who have had thyroidectomy and ablation of any remnant tissue with radioactive iodine. This regimen can also be used to stimulate iodine uptake by malignant cells in a total body scan (see below). 

Alternatively, if huge numbers of livestock are kept on a large area of pasture, parenteral supplementation may be preferable. For example, iodine supplementation provided by an intramuscular injection of a slow release preparation, such as iodized oil, can be sufficient for several months (Chambon and Chastin, 1993). Parenteral administration of iodine is beyond the scope of this chapter and only dietary supplementation of iodine is discussed here. 

In KBD subjects, the evolution of thyroid function after correction of iodine was similar in selenium supplemented and nonsupplemented subjects. This finding corroborated previous studies, suggesting only a moderate effect of selenium deficiency on thyroid hormones in human (Calomme et al, 1995 St. Germain and Galton, 1997). In Tibet, the administration of an intramuscular injection of 475-mg of iodine to KBD subjects was sufficient to correct iodine deficiency for 16 months, because at this time serum T3 increased again to pre-iodine levels and mean iodine urinary concentrations had fallen... 

In order to resolve the controversy over the role of iodine in the pathogenesis of the nervous type of cretinism observed in Papua New Guinea, a double blind controlled trial was carried out using a single intramuscular injection of iodinated oil. This had previously been shown to be an effective prophylactic for endemic goitre. ... 

In developed countries where there is a risk of iodine deficiency, supplementation of foods is common. Iodized salt may be available, or bread may be baked using iodized salt. In developing countries, such enrichment of foods is not generally possible, and the treatment and prevention of iodine deficiency depends on periodic visits to areas at risk by medical teams who give relatively large doses of iodized oil by intramuscular injection. 

Prevention of goiter may sometimes be achieved in endemic areas of developing countries by the intramuscular injections of iodized oil once every 2 to 3 years. However prevention of goiter is usually achieved in the developed countries by the use of iodized salt (3 g of which furnishes 228 meg [micrograms] of iodine or slightly more than the Recommended Dietary Allowance [RDA] of 200 meg per day for lactating women). Most people use more than 3 g of salt per day. 

This situation is observed in coxmtries where the prevalence of goiter does not exceed 10 to 15 % of the population and also in previous endemic areas where subjects have been treated by intramuscular injections of iodized oil. The urinary iodine concentration is usually borderline low while circulating levels of T3, T4 and TSH are still normal. 

The results, reported in table 1, clearly demonstrate that after oral or intramuscular administration of 1 g iodine per kg bodyweight, about 1 to 2 % of the radioactive iodine is incorporated into the thyroxine 7 days post injection. 

Laboratory animal studies clearly demonstrate that when administered by the oral route, Lipiodol is rapidly and largely absorbed, approximately 70 % of the dose being eliminated in the urine within 3 months. This absorption was indicated by a marked and quite prolonged (several days) appearance of iodine in the blood. It caused a radioactive iodide incorporation of 1 - 2 % of the injected dose in T4 thyroxin, for both oral or intramuscular route. 

These results are grossly consistent with those obtained by JUN and JIANQUN in Guinea pigs with soybean iodized oils. These authors reported a 80 % urinary and fecal elimination of the oral dose within the 3 days post administration. 12 % of the dose is detected 7 days post injection in the whole body and rapidly eliminated from the fat storage sites. The author hypothetized a rapid deiodination occuring in the gastro intestinal tract and in the body. They did not conclude about the thyroid iodine uptake. However, our study demonstrated that unless a few percent (6 % at 7 days and less than 2 % at 90 days) of the injected dose is retained in the body, a similar iodide incorporation in T4 is observed for oral and intramuscular administration route at least 7 days post injection. No conclusion can be drawn about delayed T4 iodine incorporation as no quantification was possible at 90 days. 

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