Abstract

Radiotracers labelled with 14C, 3H, 125I are used in vivo (studies onADME, mapping tissue distribution/dosimetry) and in vitro (radioligandreceptorbinding) as investigative tools in drug development (DD) andrelated research to screen and select potential drug candidates.Advances in instrumentation in performing quantitative whole bodyautoradiography and nuclear imaging of small animals (SPECT, PET)using short-lived radiotracers (18F, 11C) have led to additional optionsin DD. Micro-dosing involves administration of a tiny fraction (usually1/100) of the intended therapy dose and containing micro to nanocurie level of radiolabelled drug in human in the early phase of DD.These techniques have high sensitivity and provide quantitativeinformation to facilitate assessment of drug efficacy and regulatoryapproval and also lead to considerable cost saving through criteriabasedselection or rejection of candidate molecules in DD. Radiotracersas radiopharmaceuticals are used to assess the efficacy of a potentialdrug, or therapy protocol, by quantitative nuclear imaging of thelesions and/or organ function in patients for early decision on the utility(or otherwise) or optimisation of the therapy.