High absorption (specific mechanism of SFC absorption)
Figure 4.
Structural formula of SFC (estimated)Sodium Ferrous Citrate (SFC), the ingredient of Sanferol®, is a soluble chelated iron (non-ionic iron) of low molecular weight in which a ferrous iron atom is chelated with two citric acids as shown in Figure 4.1) Chelated bonds, consisting of multiple bonds such as an ionic bond and coordinate bond, are more stable and less dissociable in a broad range of acidic to basic pH values than ionic bonds.
Iron is mainly absorbed from the small intestine, particularly from the duodenum and the superior portion of the jejunum. SFC dissolves in a broad range of acidic to basic pH values. In particular, in weak acidic to basic pH range of the gastrointestinal tract, it is present in the form of a low-molecular weight chelated iron complex enabling intestinal absorption, unlike ferrous sulfate and ferrous fumarate, which two compounds form insoluble high-molecular weight polymers resistant to absorption. Thus, SFC is absorbed readily in the intestinal tract.8)9)
As shown in Figure 5, SFC is present in the following two forms in the weakly acidic pH of the upper gastrointestinal tract and is absorbed predominantly as chelated iron in the small intestine (mainly the duodenum) through the mucosa to the serosa:8)
(i) Chelated iron (non-ionic iron) consisting of iron and citric acids
(ii) Ionic iron dissociated from chelated iron
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Figure 5. Mechanism of SFC absorption (estimated)
SFC has the characteristic mechanism of absorption as shown in Figure 5. Because of the features described above, SFC is expected to have higher absorption than other iron materials such as ferrous sulfate and ferrous fumarate, and ferrid pyrophosphate.
References:
- 1)
- Ishino Y, Takashima M, Terashima C, Orimo Y (1988). Physicochemical properties and stability of tetrasodium biscitrato iron (II). Pharmaceutical Regulatory Science 19(1):44-52 [English Translation].
- 8)
- Fujita T, Terato K (1973). Approach to mechanism of intestinal iron absorption in terms of physicochemical properties of iron compounds. J of Clinical and Experimental Medicine 87(13):711-716 [English translation].
- 9)
- Terato K, Fujita T, Yoshino Y (1973). Studies on iron absorption. I. The role of low molecular polymer in iron absorption. Am J Dig Dis 18(2):121-128 [English translation].
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