Methylenediphosphonate complexes

A complete understanding of why specific metal complexes target certain tissues has yet to be achieved, but would be extremely valuable for the rational design of new radiopharmaceuticals. Complexes of 99mTc vvilli diphosphonates, e.g. methylenediphosphonate, localize in bone and especially in areas of disturbance of bone metabolism, such as tumours thus they may be used to map the presence and location of bony metastases from various types of cancer. Chelates such as "Tc-DTPA may be used to study differential renal function in the kidneys or to monitor the function of a transplanted kidney. Attachment of chelating groups, often based on DTPA, to antibody proteins permits the formation of Tc- or in-labelled antibodies for tumour localization. 

Another group of compounds which has been investigated is the substituted methylenediphosphonates. Values of the dissociation constants for the calcium complexes reported in the literature, and some recently determined values, are presented in Table 5. 

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