MULTIDISCIPLINARY science is all the rage these days. Even so, the synergies between archaeology and pharmacology are not, at first sight, obvious. But there is a connection. An analytical technique developed for the former, to work out how old things are, is now being used in the latter, to discover, before expensive clinical trials are undertaken, whether promising drugs are likely to fail.

At the moment, a third of drug candidates do not pass such trials. This may be because they fail to reach the part of the body where they are intended to work many molecules, for example, cannot cross from the bloodstream into the brain. Or it may be that the body breaks down the active ingredients before the drug has time to act.

Identifying such problems early in the testing process would be a boon. Trials on animals can help, but how other species react is not always a good indication of how people will. What is needed is a way of testing potential drugs on people, but in a way that cannot possibly cause any harm. That is where the archeologists come in.

For decades, archaeologists have used a technique called carbon dating to work out how old their finds are. Some of the carbon dioxide absorbed by plants during photosynthesis is radioactive. That is because it contains carbon atoms which are heavier than run-of-the-mill carbon, and are thus unstable. The radioactive carbon atoms weigh 14 atomic units, whereas the more usual ones weigh 12 units. Food grains, scraps of cloth, bits of wood and so on can thus be dated by finding out how much radioactive carbon is left in them: the less there is, the older they are.

To measure this, archaeologists use a device called an accelerator mass spectrometer. This machine shatters minuscule amounts of a sample into its component atoms, ionises those atoms in order to give them an electric charge, and then uses that charge to attract the atoms along a tube. As they travel, they are deflected by a magnetic field. Light ones are more easily deflected than heavy ones, so the two forms of carbon get separated, and when each atom reaches a detector at its expected arrival spot, it can be counted. The technique is so sensitive that it can detect one radioactive carbon atom hiding among a quadrillion ordinary ones.

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.