HEDP

The second class, Tc-essential radiopharmaceuticals, contains those Tc-labeled substances for which the Tc atom itself greatly influences the overall physical and chemical properties of the labeled substance. The biodistribution of the 5 Tc-complex of these substances is often markedly different than the biodistribution of the substance when it is not labeled with 99 Tc. The best understood example of this class of compounds is 

From there, Tc(HIDA)2 was excreted into the bile and eventually into the intestines. Loberg also prepared C-labeled HIDA and determined its biodistribution. In marked contrast to 99 Tc(HIDA)2, C-HIDA is excreted rapidly and almost exclusively by the kidneys (7 ). The difference in distribution between HIDA and the Tc-complex of HIDA demonstrates that 5 Tc is not functioning as a tag for HIDA and illustrates some of the difficulties encountered when trying to design Tc-radiopharmaceuti-cals based on small molecules (i.e. Molecular weight 1000). 

Other members of this class of radiopharmaceuticals are listed in Table I. Although the biodistribution of some of these 9gmiTc-complexes could be predicted a priori, based on a knowledge of the fate of other metal complexes of the same ligands, it is generally difficult to predict the biodistribution of Tc-complexes when one has only a knowledge of the vivo fate of the uncomplexed ligand. 

ACS Symposium Series American Chemical Society Washington, DC, 1980. 

There are two fundamental areas where knowledge must be improved before greater studies can be expected in the development of new agents. 

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Phosphonates, especially aminotri(methylenephosphonic acid) (ATMP) and l-hydroxyethylidene-l,l-diphosphonic acid (HEDP). Organophosphonates have the ability to control both scaling and corrosion by a combination of chelation and crystal nuclei growth supression (threshold) mechanisms they also provide scale control by crystal distortion. 

In addition, the sodium salts are metastable at best, producing white precipitates unpredictably and thus making formulatory work difficult. (It is also more expensive than ATMP.) HEDP has a sequestration value of 843 mg CaC03/g product at a pH level of 11. The tetrasodium salt has a MW of 294. Examples include Dequest 2010/2016, Mayoquestl500, Phos -6, Briquest ADPA 60A, Unihib 106, and Sequacel HD. 

Where variable FW quality requires the benefit of additional chelation and EDTA and NTA are not appropriate, add ATMP to the formulation. It is suitable for up to 700 psig. However, where steam comes into contact with food only HEDP can be employed. The pressure limitation for HEDP is 400 psig. 

Phosphonates. Various phosphonates, such as 1-Hydroxyethylidine-l,l-diphosphonic acid (HEDP), have been... 

When there is a limitation of the phosphorus content in detergents of 1%, then addition of phosphonates can act as an alternative solution in combination with other polyvalent ion-binding substances. Especially when magnesium is a cause of water hardness the zeoliths can form precipitations. But phosphonates, like hydroxyethanephosphonic acid (HEDP) and ethylenediaminetetra-methylenephosphonic acid (EDTMP), are able to sequester magnesium ions as well. 

Phosphonates are often used in detergents as stabilizers for encymes and bleaching components in a concentration of <0.5%. Dates of acute aquatic toxicity of the most used substances HEDP, aminotrismethylenephosphonic acid (ATMP), and EDTMP are given in Table 14. In a concentration of <2 mg/L no remobilization of heavy metals from sediments was observed [207]. 

Re Complexes for Treating Painful Bone Cancers - Re-HEDP, MDP... 

Under the strongly alkaline conditions of mercerising, addition of either gluconate or triethanolamine with a little HEDP is useful. The presence of a polycarboxylate helps to prevent precipitation on machine components. 

Hydroxyapatite particles can be used for radiation synovectomy by exploiting the strong binding of rhenium diphosphonate complexes to the surface of hydroxyapatite (vide supra). The same 186Re-HEDP preparations as for bone palliative therapy are used. When injected into joints, these particles (mean diameter 25 pm, maximum diameter 45 pm) remain within the joint to the extent of at least 95% for several days in arthritic rabbits and rats [156], More recently, microspheres have been labeled with 188Re for this purpose [156a,b],... 

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