What is a medical drug? Ask anyone on the street and they’ll probably tell you what kind of job you take when you’re not well.
This understanding is wrong, as we shall see. But after thorough investigation, my colleagues and I found that other potential definitions were no better.
Despite their centrality to medicine, we have no idea what medicinal drugs are. We can’t even tell the difference between drugs and food, let alone drugs and so-called natural alternatives.
Definition of Goldilocks
In a recent article in the Journal of Medicine and Philosophy, my colleagues (Sarah Linton, a pharmacist, and Maureen O’Malley, a philosopher of biology) and I attempted to outline a viable definition of medicinal drugs.
A viable definition should be broad enough to include anything classified as a drug. To make sense of all this, we used the drug bank compiled by the Canadian Institutes of Health Research, which lists more than 16,000 substances.
The definition should also be narrow enough to exclude substances that are not normally considered drugs. Take food, for example. Eating a sandwich is usually never considered drug taking.
In short, a viable definition of what drugs are should occupy a Goldilocks zone between these two requirements: large enough to include all drugs, small enough to exclude everything else.
Based on an initial study of pharmacology textbooks, we found three broad ways of defining drugs: in terms of what they are, how they work, and what they are used for.
Unfortunately, none of these options fall into the Goldilocks zone.
Are drugs specific chemicals?
If all drugs were a certain type of chemical, then defining drugs would be easy. But this idea is hopeless: there is nothing in common, chemically speaking, all drugs have in common.
It’s also tempting to think that drugs are man-made chemicals, made in a lab, while natural supplements come from nature, and that’s the difference.
But many medicines are natural in this sense. Aspirin, for example, is obtained from willow bark.
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This has immediate implications for so-called natural supplements such as fish oil.
If drugs are chemically indistinguishable from natural supplements, supplements should not be considered a safe alternative. Supplements are no more or less safe than many drugs.
Do the drugs perform a specific function?
Perhaps drugs can be defined in terms of what they do. This idea initially seems promising, as many drugs work by binding to receptor molecules in the body.
Think of a lock and key: the receptor molecule is the lock, and the drug is the key that opens it.
The discovery of receptor molecules is significant. For some, that’s the big idea of the science of pharmacology.
But this definition of medical drugs is also hopeless. Many drugs do not bind to receptors. Antacids, for example, work simply by changing the level of acidity (pH) in the human body.
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Many placebos also bind to receptors. Placebos are often compared to drugs, but defining drugs as things that bind to receptor molecules would include a lot of placebos in the definition. So this definition won’t work either.
Is there a way to define placebos that clearly differentiates them from drugs? This is not obvious, because defining a placebo is also quite difficult.
For example, placebos can be thought of as substances that have no therapeutic effects. But placebos can have therapeutic effects (the so-called placebo effect), so this definition won’t work. A number of other definitions face similar problems.
Our research paves the way to explaining why placebos are so difficult to define. To properly define placebos, we need to distinguish them from drugs, which we cannot do without a definition of what drugs are.
Drugs make me better
This brings us back to health. According to this view, a drug is just any chemical substance used in medical treatment.
This is better: it covers the whole range of substances used as drugs in a medical context.
But now there is absolutely no hope of keeping food and nutrients out.
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Consider, for example, total parenteral nutrition. This is a chemical infusion given to people who have trouble absorbing nutrients in the normal way.
Full parenteral nutrition is used in medical treatment. But what it does for your body isn’t really that different from what a good sandwich does.
Any treatment-based drug bill inevitably erases the food contrast.
In our daily lives, we make choices that rely on an implicit understanding of what drugs are.
For example, we take paracetamol because it is a medicine. Many of us may also take fish oil precisely because we believe it is not a cure.
Without an understanding of what medicines are, we risk making serious mistakes.
We can take substances that we think are inert (placebos) because they are natural (like fish oil), when in fact they are active drugs.
Similarly, all drug legislation assumes that we already know what a drug is.
But we don’t: our understanding is clearly evolving. This means that regulation must also be constantly changing. Considerable resources must therefore be devoted to rewriting the legislation as we continue to think about what medical drugs are, as the recent reclassification of MDMA and psilocybin as drugs in Australia shows.
Then there is food. Food is not administered or regulated as medicine in a hospital, with the exception of total parenteral nutrition and similar substances.
But if doctors use food as medicine to contribute to a patient’s well-being, then perhaps it should be subject to the same standards.
This may require a radical rethinking of the way meals are provided in hospital. Perhaps meals should be administered and regulated with the same care as drugs.
Hospital lunches may never be the same. But that can be a good thing.
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