Metabolism studies, objectives

Plant metabolism studies will provide information on the absorption, translocation, dissipation and degradation of the agrochemical. This information defines the residual analytes of regulatory concern that could include either the parent compound or metabolites in the field crops. Plant metabolism studies should be conducted with at least three crop representatives of three different crop groups listed in Table 1. One of the major objectives is to determine the comparative metabolism of the agrochemicals between animals and plants among different plant species. MAFF approves metabolism studies that are conducted in foreign countries, which should be operated under the certified GLP system. 

The first step is to identify the critical crops and the compounds for which residue studies must be conducted. The breakdown and reaction products and metabolites in treated plants and products are often identified after treatment with a C-14 labeled test substance in plant metabolism studies. The objective is to determine the fate of the parent substance and its metabolites in the crop plants and their processing products. From the results of the studies, the relevant residues are defined residue definition). For example, in plants glyphosate is converted to its main metabolite AMPA (= aminomethylphospohonic acid), which was also studied as part of the residue assessment. 

In LC/MS metabolite profiling and identification analysis, other liquid chromatographic detection formats, including UV, radiodetection, and NMR, are often employed to facilitate metabolite detection, quantification, or structural characterization. These liquid chromatographic detection formats provide high analytical values that are complementary to mass spectrometry and critical to accomplishing objectives of drug metabolism studies (Zhu et al., 2009). 

The overall objective of clinical trials is to establish a drug therapy that is safe and effective in humans, to the extent that the risk-benefit relationship is acceptable. The ICH process has developed an internationally accepted definition of a clinical trial as Any investigation in human subjects intended to discover or verify the clinical, pharmacological and/or other pharmacodynamic effects of one or more investigational medicinal product(s), and/or to identify any adverse reactions to one or more investigational medicinal product(s) and/or to study absorption, distribution, metabolism and excretion of one or more investigational medicinal product(s) with the object of ascertaining its (their) safety and/or efficacy. ... 

Any investigation in human subjects intended to discover or verify the clinical, pharmacological and/or other pharmacodynamic effects of an investigational product, and/or to identify any adverse reactions to an investigational prodnct, and/or to study absorption, distribution, metabolism, and excretion of an investigational product with the object of ascertaining its safety and/or efficacy. 

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