Half of my family is in medicine.
NONE of them trust anything until it's been out for 10-30 years.
The first decade a medicine is out it's still in it's testing phase. In the US we have very very SMALL (and short) human trials (following years and years of animal trials). One a medicine comes out, THAT'S when we find out how it really works. And we don't find that out for a solid 10 years. At 5 years we've got a good idea how it usually works, but the 10 year mark is when we know, absolutely, what all the various side effects are.
ALSO what a medication is best for.
The way drug companies work is this: The have a best selling ________. So they don't develop more of that for some time... years and years (antidepressants, blood pressure, etc.). They have no desire to compete against themselves. At the 10 year (ish) mark we solidly know what a medication is really best for. Which is why one may be prescribed something "off label" for a condition. Because the med that works BEST was actually designed for something else. It is INCREDIBLY RARE for a drug company to spend the 10's of millions to 100's of millions to 'relabel' a med (the heart medication Viagra... for example... is no longer labeled as a heart medication!)
All research scientists, healthcare professionals (or at least the ones who paid attention in school), and health or science student KNOW that the first 10 years is Phase TWO Human Trials.
Good healthcare professionals take note of all their patients' side effects and send that information out to the medical community. Eventually they all get compiled into the PDR.
Oh.... The 30 year mark? That's when we know the long term effect of a medication.
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My doctor is absolutely superb. I had to go through 9 or so new primary care providers in order to find him. I have total trust in him. In no small part because as a superb doctor he farms out any area he is not expert in AND is linked in with a network of other superb doctors and surgeons. Birds of a feather.