Iodine in biology
The U.S. Institute of Medicine (IOM) updated Estimated Average Requirements (EARs) and Recommended Dietary Allowances (RDAs) for iodine in 2000. For people age 14 and up, the iodine RDA is 150 μg/day; the RDA for pregnant women is 220 μg/day and the RDA during lactation is 290 μg/day. For children 1–8 years, the RDA is 90 μg/day; for children 8–13 years, 130 μg/day. As a safety consideration, the IOM sets tolerable upper intake levels (ULs) for vitamins and minerals when evidence is sufficient. The UL for iodine for adults is 1,100 μg/day. This UL was assessed by analyzing the effect of supplementation on thyroid-stimulating hormone. Collectively, the EARs, RDAs, AIs and ULs are referred to as Dietary Reference Intakes (DRIs).
Indocyanine green
Because the preparation contains sodium iodide, a test must be carried out for iodine intolerance. Because around 5% of iodide is added, the iodine content of a 25 mg ampoule is 0.93 mg. In comparison, preparations for a bone marrow CT (140 ml) contain 300 mg/ml and for a corona angiography (200 ml) 350 mg/ml of iodine. ICG has the ability to bind 98% to plasma proteins – 80% to globulins and 20% to alpha-lipoprotein and albumin – and thus, in comparison with fluorescein as a marker, has a lower leakage (slower emergence of dye from the vessels, extravasally). Because of the plasma protein binding, ICG stays for up to 20–30 minutes in the vessels (intravasally). When the eye is examined, it thus stays for a long time in tissues with a higher blood flow, such as the choroid and the blood vessels of the retina.