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Metabolism of 99mTc- l,l-Ethyl cysteinate dimer in healthy volunteers
Ist Teil von
Neuropharmacology, 1991-03, Vol.30 (3), p.283-292
Ort / Verlag
Oxford: Elsevier Ltd
Erscheinungsjahr
1991
Quelle
Elsevier Journal Backfiles on ScienceDirect (DFG Nationallizenzen)
Beschreibungen/Notizen
99mTc-
l,l-Ethyl cysteinate dimer (ECD) is a brain-perfusion imaging agent, which exhibits selective retention in brain and rapid renal excretion. The pharmacokinetics and metabolism of ECD were studied
in vivo in healthy humans and its metabolism
in vitro was evaluated in tissue from human brain.
In vitro studies showed
99mTc-
l,l-ECD to be metabolized to a polar
99mTc-complex. It has been shown previously that most of the activity of
99mTo retained in the brain of the monkey
in vivo is in the form of a polar
99mTc complex (Walovitch, Hill, Garrity, Cheesman, Burgess, O'Leary, Watson, Ganey, Morgan and Williams, 1989). Whole body images of the distribution of
99mTc-
l,l-ECD (10mCi i.v.) in four adult males showed good uptake in brain, with slow elimination (6.8 ± 0.3% injected dose [mean ± SE] at 5 min), with less than 25% decrease in activity during 4 hr of imaging. Background areas in the head and lungs washed out rapidly, providing ideal imaging conditions. Elimination of
99mTc from venous blood was biphasic, with a plateau of activity between 2–15 min (7–8% injected dose) before a terminal phase, with a
t
1
2
of a few hours. Organic extraction of whole venous blood showed greater than 50% of the
99mTc-
l,l-ECD to be in the form of polar metabolite(s) at 5 min. They were identified in the urine as the
99mTc ethylenediylbis-
l-cysteine, monoethyl ester complex (ECM) and the
99mTc-ethylenediybis-
l-cysteine complex (EC). These metabolites were excreted rapidly (75% injected dose in urine within 6hr).
The results of this study support the hypothesis that the selective retention in brain, rapid blood elimination and renal excretion of
99mTc-
l,l-ECD is due to its metabolic transformation to polar end products.