On Sat, 8 Oct 2022 17:47:15 +0200, Athel Cornish-Bowden
<
acor...@imm.cnrs.fr> wrote:
>On 2022-10-08 15:07:58 +0000, Peter Moylan said:
>
>> On 09/10/22 01:55, Peter T. Daniels wrote:
>
>>> Didn't Asimov teach me, long, long ago, that we can't assimilate the
>>> "wrong" isomers of things? I don't remember whether they'd be
>>> harmful, or just pass through the gut.
>>
>> They just pass through.
>
>It's not as simple as that. Some, like L-glucose, just pass through;
>some, like L- and D-lactic acid, are pretty much interchangeable; some,
>like L- and D-carnitine, differ a lot in toxicity, and D-carnitine, for
>example, should not be used as a medicine.
>
>> A benefit to dieters.
There was at least one psychoactive medicine for which one
isomer had the expected benefit, and the other lacked the
effectiveness and resulted in "side-effects" instead.
(It might have been chlorpromazine but I couldn't confirm that
with a few minutes of Googling.)
As I recall it, the original manufacturer used a method that
produced (as it happened) only a single isomer, and that was
what was proved good in clincal trials, and no one had paid
much attention to chirality (right word?). When the patent
expired, another manufacturer produced its version differently,
and both isomers resulted. The new product was less effective
and had new side effects. I think that they were more surprised
by the side effects than by the lowered effectiveness -- being
potent-but-bad is more complicated than just-passing-through.
In the short run, this encouraged manufacturers to /discourage/
customers from buying off-brand versions of their once-proprietary
drugs: "You don't know, for sure, that it is exactly the same thing."
In the longer run, the FDA had to adapt to the more complicated
reality. I don't remember details of that.
--
Rich Ulrich