A few years ago researchers at the Lawrence Livermore National Laboratory, in California, realised that accelerator mass spectrometers tuned to detect radioactive carbon might be adapted to see how drugs survived in the body. This would be done by including a few radioactive carbon atoms in molecules of the drugs in question. That has now happened. Volunteers are given tiny traces of a radioactively labelled drug too small to harm them, and typically just a hundredth of the estimated full dose in a drink. They are then kept in hospital for two or three days while blood samples are taken every few hours. Their urine and faeces are also collected.
By examining these samples for the presence of radioactive carbon, the developer of a particular drug can see whether the active ingredients are absorbed into the body and, if they are, how long they persist there. If they do get absorbed and then persist, the drug is probably worth developing further. If not, then it can be abandoned before any more expensive tests are conducted. And by using people rather than experimental animals for the tests, the researchers can be confident that the results are applicable to humans.
The regulatory authorities in America, Europe and Japan have welcomed the idea of microdosing, as the technique is known, and are developing guidelines for its use. Meanwhile, a number of companies have already been established to offer the technique to drug firms. One of them, Xceleron, which was formed by scientists from the University of York, in England, has already tested 40 molecules and has recently signed contracts with several large drug companies. Given the difficulties and delays involved in developing new drugs, microdosing could prove a shot in the arm for pharmaceutical companies.
