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Comment by colechristensen | Hacker News Reader

>it seems like they dont have any idea of why it works but are pretty sure it does

This is true for a large volume of medical treatments

Is this really true? That we don't know, or only have a very vague idea about the pharmacodynamics, or simply the mechanism of action of various treatments, so the process is more about establishing that they aren't harmful?

From what I've read about some medicines it's something like "We originally used it for this but it turns out it stops this too! (we're not entirely sure why)"

Off-label prescription is prescribing a drug for non-intended purpose.

Viagra for example, was originally studied for high blood pressure.

I've also seen a tv program where they visited a pharmacy company's lab that's literally machines mixing random drugs in order to find their next product. The place was the size of a walmart.

You may have heard that many medicines are found by testing untold number of Amazonian species for medicinal properties. That sort of search finds things that work, not the reasons why.

We know the basic mechanism of action behind SSRIs, but you'd be hard pressed to find anyone that can tell you definitively why they can be effective.

They are some of the most prescribed drugs in America. They have a better safety profile than MAOIs, despite that the latter can be more effective in treating depression / anxiety.

There was a theory behind why SSRIs work that existed when they were developed (the serotonin theory of depression), but this theory was later shown to be wrong - basically, SSRIs do modulate serotonin but that has no relation to whether you are depressed; if SSRIs do work, its through another mechanism. In addition the efficacy is greatly overstated; large follow-up studies have shown that they only have measurable effects on the most severely depressed individuals. The vast majority of people being prescribed SSRIs do not fall in this category and likely receive no benefit beyond placebo.

This, of course, highly depends on what your definition of "severely depressed" is. There are several standards whose ranges don't even overlap on the same scale. [1] Also consider that people who have moderate depression may have episodes that put them in the severe category, which we would like to treat effectively.

[1]: http://slatestarcodex.com/2014/07/07/ssris-much-more-than-yo...

Best example - aspirin. We know it works - but we have no clue how exactly.

The important part in your comment is "exactly", because we know quite a bit about its mechanism of action.

https://en.wikipedia.org/wiki/Mechanism_of_action_of_aspirin

But we didn't know any of this when we started using aspirin as an analgesic.

Well, yeah, willow bark was already used in antiquity to treat pain.

It is a COX-2 inhibitor. The mechanism is fairly well understood. I don't think anyone in the area would say no clue.

By happy coincidence, I was reading this yesterday - http://blogs.sciencemag.org/pipeline/archives/2016/01/26/med...

> The FDA does not actually require you to have a mechanism – that’s a common misconception. The FDA wants to see safety and efficacy. Now, a known mechanism will probably make the assessment of both those factors easier, to be sure, so all things being equal, you’d rather know how your drug works.

There are several treatments the working principles of which we have more or less no idea about.

The process is extracting active compounds, establishing that they do something (and if so what), finding out whether there are safe dosages, charting what these safe dosages are and looking for a way to mass-produce the compounds.

I've seen more than one prescription-drug commercial on TV that uses the fine print (sometimes even the voiceover!) to say "we don't know how or why this drug has the effects it does".

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