A lot more complicated

Cells in early human embryo

The great Bad Science blogger, Ben Goldacre, once produced teeshirts proclaiming: ‘I think you’ll find it’s a bit more complicated than that.’

It’s a sentiment that can be applied to just about every medical story, and one that may yet lead us in some weird directions. On Monday, I was at the Royal Society, to hear biologist and Nobel Prize winner Sir Paul Nurse speak about ‘great ideas’ in biology.

Sir Paul talked us though the development of our knowledge of the cell as the building block of life. He explained that our current approaches to disease management through drugs is somewhat like hitting a machine with a hammer, because we simply don’t know enough about how the cell works. Millions of chemical reactions take place in this microscopic entities, each having a knock-on effect on the next, creating positive and negative feedback mechanisms we have no idea about.

Which is why, when you think you’re making a drug to prevent heart attacks, you end up with one that cures impotence. Sir Paul predicted that biology could be approaching its quantum moment, when everything we thought we know suddenly gets too complex for common sense.

I was thinking about this as I read, with increasing alarm, about a new study looking at the catastrophic interaction of two commonly-used drugs. One, tamoxifen, is a mainstay of breast cancer treatment. The other, the antidepressant paroxetine, is used to treat depression, anxiety – and the side effects of breast cancer treatment.

Not surprisingly, quite a lot of women taking tamoxifen to treat breast cancer are also prescribed antidepressants. Many of them are prescribed paroxetine. Unfortunately, the study showed pretty persuasively that paroxetine stops tamoxifen from working. The end result is that women taking both drugs have a massively increased chance of dying from their breast cancer, instead of being cured.

Its frightening to consider how many women may have conscientiously taken the two drugs, trusting in their doctors that they’re doing the right thing, not suspecting that one was cancelling out the effects of the other. And it angers me to discover that the potential for this interaction has been known for some time. Other antidepressants may not have the same effect. So why, for heaven’s sake, was this one still used? I expect someone will tell me it’s not as simple as that.

Image: From Wellcome Images, with CCL.

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