While reading The Three Body Problem by Liu Cixin, which I am enjoying very much, I fell into a Wikipedia rabbit hole.

I wanted to read more about our Sun, this led me to reading a bit about nuclear fusion which in turn made me read a bit about deuterium which then sent me indirectly to this paper about the 'D Switch'.

Di Martino, R.M.C., Maxwell, B.D. & Pirali, T. Deuterium in drug discovery: progress, opportunities and challenges. Nat Rev Drug Discov 22, 562–584 (2023). https://doi.org/10.1038/s41573-023-00703-8

Deuterium is an isotope of hydrogen. If hydrogen's nucleus is made of a single proton with no neutrons, deuterium has a proton and a neutron. It is stable and doesn't pose any radioactive risk to humans. It is just rare on Earth.

The D Switch is also called deuteration which is a fascinating way to modify the pharmacokinetic profile of common drugs. One or more hydrogen atoms in a common drug is substituted with deuterium. Apparently this modification slows down the metabolism of the drug thus prolonging its effect.

Already several D compounds were approved (e.g. deutetrabenazine for chorea and tardive dyskinesia) and several modified neurological and psychiatric medications are being clinically trialed.

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