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Technical guidelines for non-clinical pharmacokinetic studies of drugs

Release time:

2014-05-13

Excerpt: Release Unit: china food and drug administration Release Date: May 13, 2014 2. Selection of Radioisotope Labeling Methods Low-energy radioisotopes commonly used in ADME research of small molecule chemical drugs are carbon -14(14C) and tritium (3H). 14C labeling is the most commonly used, its biological background is low, biology almost no isotope effect and affect metabolism, rarely occur isotope exchange, sensitivity is higher than 3H and easy to quantify. Metabolically stable sites should be selected when labeling carbon -14 compounds. In vivo testing unless 14C labeling is very difficult or

Excerpt: Release by: china food and drug administration Release date: May 13, 2014
 
2. Selection of radioisotope labeling methods
The low energy radioisotopes commonly used in the study of small molecule chemical drugs ADME are carbon -14(14C) and tritium (3H). 14C labeling is the most commonly used, its biological background is low, biology almost no isotope effect and affect metabolism, rarely occur isotope exchange, sensitivity is higher than 3H and easy to quantify. Metabolically stable sites should be selected when labeling carbon -14 compounds. In vivo testing, 3H labeling is selected unless 14C labeling is very difficult or impossible to label, and very low doses require very high specific activity. 3H labeling is relatively simple and has higher specific activity than 14C labeled compounds, which is especially suitable for low-dose administration of compounds or early biotransformation research. Similarly, when tritium labeling compounds, metabolic stable sites should also be selected as labeling sites, and non-localized tritium water exchange labeling methods are not recommended.
The radiochemical purity and chemical purity of 14C and 3H labeled compounds should generally be ≥ 95%, and do not contain> 1% of a single impurity.

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