Radiolabeling 101: 4 Common Compounds Used In Drug Development


Everybody has seen those commercials for new drugs. Whether they’re treating depression, fibromyalgia, or a chronic illness, they all had to go through the same development process; from its original synthesis to the extensive FDA trials, odds are radiolabeling was used at some point.

It’s vital that scientists and researchers are able to see where their drug is in the human system and whether or not it’s doing what it’s supposed to be doing. When drugs undergo radiolabeling, they are blasted by a radioactive tracer; this chemical compound has had one or more of its atoms replaced by a radionuclide so that its radioactive decay can be measured.

This is easier to trace because radioactive decay is much more energetic than simple chemical reactions; even if the radioisotope is present in low concentrations, it can still be detected. Essentially, radiolabeled compounds can be used to explore the mechanism of chemical reactions by tracing the path that the radioisotope follows from reactants to products. Radioisotopes from a number of elements are used in these trace experimentations. Let’s take a look at the four elements favored for biochemical reactions.

  • Hydrogen: Tritium is a radioactive isotope of the element hydrogen. It possesses a half-life of around 12.5 years and experiences beta decay. Hydrogen is popular in biochemical studies because it is found in all organic compounds.
  • Carbon: 14C labeling (C14 radiolabeling) also experiences beta decay, but the half-life is significant at around 5,730 years. Because it is continuously produced in the upper atmosphere of the planet, it occurs at a trace level in the environment. 14C is very popular when scientists needed to trace the progress of organic molecules through metabolic pathways.
  • Sulfur: Yet another beta decay with a half-life of 87.5 days, sulfur is used to label the sulfur-containing amino acids methionine and cysteine.
  • Phosphorus: Phosphorus radioactive tracers experience a half-life of 14.29 days. They are used primarily to study protein phosphorylation by kinases in biochemistry.

The next time you’re channel surfing mindlessly and come across one of those generic drug commercials, try to remember this process. When you have an understand for just how nuanced and complicated (and long) drug development is, those commercials become a lot more interesting.

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