Molecules, Medicines, and Mental Health


There’s been a ton of media recently trying to raise awareness about sufferers of mental health issues. From helpful infographics comparing mental and physical ailments, to exposés of the state of mental health treatment under the NHS. Despite this very welcome progress, one relatively under- reported feature of mental wellbeing is drug information. Explanations of what different drugs are, and how they work are often left out.

Whilst reading about various medications for depression, I came across some information that seemed so important to everyone who has ever handed in a prescription, that I couldn’t help but dedicate an article to explaining a worrying trend among available pharmaceuticals. Now don’t get me wrong: I’m not some kind of “anti-vax” lunatic who has it in for any and all companies who choose to make a profit off their tablets. Please don’t get the idea I’m writing this out of some kind of vendetta. Instead consider this something I’m really eager for more people to understand for no better reason than it will (hopefully) help some folks make more informed decisions when their Doctor offers them a choice of pill for what ails them. Finally let me add that I’m by no means an expert on this: I’m just somebody with a vested interest and a habitual need to research things I find interesting. Let’s get cracking.

The first thing we need to get our heads round is some of the chemistry of the massive molecules that make up the chemicals in medication; not in any great detail, just one principle idea. The chemicals in drugs (and in all organic life) are typically enormous tangles of Carbon atoms with many branches, loops, and extra elements stuck on in different places; the kind of thing that gets drawn to look like a fragment of a weird alien language.

Large organic molecule
This one spells “Oh dear God no”

Some of these massive tangles have a weird quirk: they have a “handedness”. If you make a pair of shoes, each shoe could use precisely the same stitching,materials, and construction in precisely the same way but only one is a mirror image of the other. That’s the same with these molecules: they can be left or right “handed”. No matter how you try and spin it round, a left-shoe will never become a right-shoe, but they’re still identical, right? They have the same parts. In chemistry this is called “chirality”.

You might reasonably assume that the various bits that make up a molecule are what’s important: how much difference can it make whether a molecule is “right” or “left” handed? It’s the same chemical, right? Actually it turns out the difference is fairly drastic. For starters, by what seems to be random chance, almost every living thing on earth uses “left handed” protein and sugar molecules. All the way from bacteria to humans, our bodies are designed to process only one “version” of these chemicals. If you got a lab to produce sugar molecules that were “right handed”, our body wouldn’t be able to do anything with them. Secondly—and here we start to move back towards the original topic of drugs—sometimes the different versions of the same chemical can affect our body in drastically different ways.

In the 1950s, a German pharmaceutical company created what seemed to be a new wonder-drug. It cured anxiety, insomnia, headaches, and—most famously—morning sickness during pregnancy. Sounds too good to be true? It turned out that only one “handedness” of the molecule in the drug (called Thalidomide, if you hadn’t already guessed) actually did what was promised, but unlike in sugars the other-handed molecule (which was part of the mixture in each tablet) didn’t just pass through the body unnoticed. The drug was pulled from shelves in 1961 after around ten thousand children were born with terrible birth-defects mostly affecting the arms. It’s estimated two thousand more babies died directly as a result of their mothers taking the drug.

So… chirality—molecular handedness—is a big deal. Whilst I was reading about the impact of chirality on drugs, I found a passage explaining that nowadays, there’s a somewhat alarming practice among pharmaceutical companies who want to make sure they keep producing new medicine. The clue was, that often medicines with only one version of a molecule (left or right handed) often begin with a prefix; for example “es”. Suddenly I was reading about something that affected me very personally.

Having been diagnosed with depression some time ago, I’ve been through a number of antidepressants before finally settling on one called “escitalopram” because it has a very small number of nasty side-effects. There’s the prefix: “es”. So I wondered: does that mean that “citalopram” (another drug I’d tried previously) has a mixture of “left” and “right” handed chemicals in it?

Indeed it does, and what’s particularly worrying is that it seems to be the case that only one version of the molecule actually works as an antidepressant. What am I getting at? There are two versions of a drug on the market—both of which might be prescribed to treat depression—and yet one of them contains a chemical mix where only 50% of the molecules in the tablet actually help you in any way. Not only that, but it turns out that the reason escitalopram (the “purer” version) has fewer side effects is that it’s believed that the other “handed” version of the molecule actively harms you.

Let that sink in for a second: it’s perfectly allowed, and accepted, that there are two versions of a drug on the market; one of which has 50% of its active ingredient as something that not only doesn’t help you, it’s actually bad for you. And this is still being prescribed.

That last part is what worries me. I completely understand that as time goes on there must be better ways to manufacture drugs and make batches of chemicals where all of them are a certain handedness. But for a company to deliberately still market the mixed version, when they know that at best only half of the chemical is doing you any good and at worst the other half is actively bad for you, should be something everyone is aware of: if not outright angry about.

None of this is new either. I’ve found a damning article about this practice in a scientific journal from 1984, but it still seems to be something relatively unknown by the general public. At the very least, this article might change that in a tiny tiny way.

If you’re a doctor, biologist, or chemist and have more to add please comment below: I’d love to have some input from experts!


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