NOVEL METHODS OF ALTERING PHARMACOKINETICS IN RADIOPHARMACEUTICAL DESIGN
Guest Editor: Hnatowich D. 

The Quarterly Journal of Nuclear Medicine 2002 September;46(3):224-32

Copyright © 2009 EDIZIONI MINERVA MEDICA

lingua: Inglese

The influence of carrier on 99mTc radiopharmaceuticals

Ballinger J. R.

Department of Nuclear Medicine, Addenbrooke’s Hospital, Cambridge, UK

­High spe­cific ­activity 99mTc-­labelled radio­phar­ma­ceu­ti­cals are ­required in ­order to ­avoid sat­u­rating ­receptor ­sites and to min­i­mise phar­mac­o­logic or ­toxic ­effects. The spe­cific ­activity of 99mTc-per­tech­ne­tate is max­i­mised by use ­shortly ­after elu­tion ­from a gen­er­ator ­which had ­been ­eluted at fre­quent inter­vals. Effec­tive spe­cific ­activity can be max­i­mised by a ­variety of ­means. ­Often is it pos­sible to ­label a ­very ­small ­amount of pre­cursor ­with a ­large ­amount of 99mTc and use the ­product ­without fur­ther pur­ifi­ca­tion; ­this is lim­ited by the ­potency of the ­ligand and the effi­ciency of label­ling, ­which in ­turn is ­affected by the ­choice of che­lator. A ­variety of pur­ifi­ca­tion tech­niques ­have ­been ­used, ­ranging ­from sol­vent extrac­tion, ­solid-­phase extrac­tion car­tridges, and ­size-exclu­sion col­umns to ­high-pres­sure ­liquid chrom­a­tog­raphy. ­Excess unche­lated ­thiol-con­taining ­ligands (e.g. N2S2, N3S) can be ­removed by a ­thiol-trap­ping ­resin. ­Finally, ­solid-­phase syn­thesis, in ­which the pre­cursor is immob­il­ised on a ­solid sup­port (­resin or ­gold) and ­only ­released ­into solu­tion ­during che­la­tion of 99mTc, is a prom­ising ­method. ­High spe­cific ­activity ­will ­become increas­ingly impor­tant ­with the ­next gen­er­a­tion of 99mTc radio­phar­ma­ceu­ti­cals.